In Re the Marriage of: Audrey Marie Chaput, petitioner, Appellant, vs. Douglas James Chaput, Respondent.

may not be cited except as provided by

Minn. Stat. sec. 480 A. 08, subd. 3 (1996).

 STATE OF MINNESOTA

 IN COURT OF APPEALS

 CX-97-2086

In Re the Marriage of:

Audrey Marie Chaput, petitioner,

Appellant,

vs.

Douglas James Chaput,

Respondent.

 Filed June 2, 1998

 Affirmed as modified

 Harten, Judge

Washington County District Court

File No. FX-95-796

Louis M. Reidenberg, Ellen E. Barton, Reidenberg, Silverstein & Barton, P.L.L.P., 625 Pillsbury Center, 200 South Sixth Street, Minneapolis, MN 55402 (for appellant)

Daniel R. Butler, Daniel R. Butler & Associates, P.A., 420 Hamm Building, 408 St. Peter Street, St. Paul, MN 55102 (for respondent)

Considered and decided by Crippen, Presiding Judge, Davies, Judge, and Harten, Judge.

 U N P U B L I S H E D O P I N I O N

 HARTEN, Judge

Audrey Chaput appeals from a marital dissolution judgment, challenging the district court's child custody determination, calculation of her income, awards of maintenance, child support, and attorney fees, and denial of her motion for a new trial. We affirm as modified.

 FACTS

Appellant Audrey Chaput ("mother") and Respondent Douglas Chaput ("father") married in 1979. They have two sons, ages 11 and 16. They began marital dissolution proceedings in 1995. In May 1997, they partially settled property distribution. They agreed that mother would keep the parties' marital homestead and the pediatric therapy business. To equalize the property division, they agreed that mother would pay father a lump sum of cash, and a series of cash payments for seven years thereafter. The parties designated this part of the property division "Level II maintenance," and specified that it was not to affect normal child support or statutory spousal maintenance, which they distinguished as "Level I maintenance." They proceeded to trial on issues of custody, Level I maintenance, and child support.

Mother owns a pediatric therapy clinic and earns in excess of $150,000 per year. An accountant/business appraiser testified that mother's personal income from business wages, plus S-corporation pass-through earnings, was $154,000 in 1994 and $215,125 in 1995. The appraiser also testified that as of August 31, 1996, mother was on schedule to earn in 1996 an amount equivalent to that earned in 1995. Father is employed as a light-duty machine operator, earning approximately $28,600 per year. The district court found that mother's net monthly income was at least $8,325 and that father's net monthly income was $2,388. Father has a workers compensation permanent disability rating of 10% from his prior occupation as an electrician. Mother lives in the parties' former home in Mahtomedi. Father lives in a townhouse in Mahtomedi.

At trial, the district court found that the parties had maintained a de facto joint physical child custody arrangement, where the children spent approximately 50% of their time with each parent. The district court ordered joint legal and physical custody of the children to formalize and continue this arrangement. It awarded father $1,000 per month in permanent spousal maintenance, $974 per month in child support, and ordered mother to pay half of father's attorney fees.

Following trial, mother filed a motion for amended findings of fact and conclusions of law, and for a new trial. Father moved to find mother in contempt of court for her alleged nonpayment of child support and maintenance. The district court denied mother's motions, but set a hearing on the contempt motion. Prior to the hearing, mother appealed.

 D E C I S I O N

 1. Child Custody

Appellate review of custody determinations is limited to whether the district court abused its discretion by making findings unsupported by the evidence or by improperly applying the law. Ayers v. Ayers, 508 N.W.2d 515, 518 (Minn. 1993). The trial court's findings must be sustained unless clearly erroneous. Id.

A district court fashions a child custody arrangement that is in the child's best interest, after considering and evaluating 13 relevant factors. Minn. Stat. § 518.17, subd. 1(a)(1)-(13) (1996). To award joint custody, a court must consider four additional factors: the parents' ability to cooperate in parenting, the parents' willingness to resolve parenting disputes, whether sole custody is detrimental to the child, and whether domestic abuse has occurred. Minn. Stat. § 518.17, subd. 2(a)-(d).

The level of cooperation required for joint physical custody has been found to exist where the parties maintain a joint custody arrangement during dissolution proceedings despite one party's contention that the parties cannot cooperate. Veit v. Veit, 413 N.W.2d 601, 605 (Minn. App. 1987). Here, despite the parties' recent inability to cooperate, they had maintained a successful joint custody arrangement from the time of separation. This supports the district court's findings that the parties could cooperate and that they could resolve disputes.

The district court's conclusion that sole custody would be detrimental to the children is supported by the district court's finding that mother would, if granted sole physical custody, interfere with father's relationship with the children and use her superior economic power to obtain her objectives.

The record contains no domestic abuse order or judgment to contradict the district court's finding that no domestic abuse occurred between the parties. Although there was some testimony that on one occasion father and mother had engaged in a physical altercation, the district court was within its broad discretion to discount this incident as isolated and stale. We conclude that the district court's award of joint physical child custody was not shown to be an abuse of discretion.

 2. Mother's Income

Findings of fact related to spousal maintenance must be upheld on appeal unless clearly erroneous. McCulloch v. McCulloch, 435 N.W.2d 564, 566 (Minn. App. 1989).

Mother asserts that in finding her gross income of $150,000 (rather than the $100,000 used by the appraiser in valuing her business) the district court altered the value of the business in the partial stipulation as to property division. When a judgment is based upon a stipulation, the stipulation merges into the judgment and it cannot thereafter be the target of attack by a party seeking relief from the judgment. Shirk v. Shirk, 561 N.W.2d 519, 522 (Minn. 1997). The judgment specifies that the parties expressly agree that the "Level II maintenance" established in the stipulated property division "shall not in any way impact or affect the issues of child support or `Level I spousal maintenance.'" If the district court was bound by the appraiser's estimate of mother's income for property division purposes, the "Level II maintenance" would affect child support and "Level I maintenance." Thus, regardless what amount the appraiser used to represent mother's income in valuing the business, the stipulation as to property division did not limit the district court's discretion to determine mother's income.

Based on all the evidence, including the testimony of the accountant and the parties' tax returns, the district court's determination that mother's minimum annual gross income was $150,000 ($12,500 per month) was not clearly erroneous.

 3. Child Support

We review child support determinations for abuse of discretion. Broas v. Broas, 472 N.W.2d 671, 673 (Minn. App. 1991).

The child support guidelines require that for two children, an obligor with income in excess of $1,000 pays child support of 30% of net monthly income. Minn. Stat. § 518.551, subd. 5(b) (1996). The district court found that father earned a net monthly income of $2,388, 30% of which is $716. Because the relevant cap on monthly income for child support purposes was $5,635, that figure was used to calculate mother's child support, rather than her actual monthly income figure of $8,325. Minn. Stat. § 518.551, subd. 5 (b), (k); Order of the Minnesota Supreme Court, March 19, 1996, C9-85-1134. Application of the 30% guidelines figure to mother's $5,635 yields $1,690 per month child support.

The Hortis/Valento formula provides the proper method for applying the child support guidelines where parents have joint physical custody. Broas, 472 N.W.2d at 673. To correctly apply the Hortis/Valento formula for child support in a joint custody arrangement where custody is shared equally (as here), each parent pays 50% of that parent's guideline amount. Id. The court then applies an offset so that the net amount paid by the parent with the higher earnings is the difference between the reduced guideline amounts. Id. Applying Hortis/Valento here, 50% of mother's $1,690 guidelines amount is $845 and 50% of father's $716 guidelines amount is $358. After mother's higher amount is offset by father's amount ($845 less $358), mother is obliged to pay $487 monthly child support, not the $974 set by the district court ($487 is half the amount ordered by the district court). Apparently the district court neglected to reduce each parties' guidelines amount by 50% (each parent has equal custody time) prior to applying the offset. We modify the district court's child support determination accordingly.[1]

 4. Maintenance

This court reviews a district court's maintenance determination under an abuse of discretion standard. McCulloch, 435 N.W.2d at 566.

First, mother contends that the district court abused its discretion in refusing to consider income father could earn by investing the "Level II maintenance" award. Generally, in determining a spouse's need for maintenance, a court should consider income that spouse will receive from his or her share of the marital property. Lyon v. Lyon, 439 N.W.2d 18, 21-22 (Minn. 1989). Here, the parties agreed that the "Level II maintenance" established in the stipulated property division "shall not in any way

impact or affect the issues of child support or Level I spousal maintenance." (Emphasis added).

The district court apparently interpreted this phrase to mean that the parties intended the "Level II maintenance" sum and its income to remain independent of support and maintenance considerations. We review de novo the district court's interpretation of a stipulation incorporated into a judgment. VanderLeest v. VanderLeest, 352 N.W.2d 54, 56 (Minn. App. 1984). And we reach the same conclusion as did the district court. The district court did not abuse its discretion in refusing to consider income father could earn by investing the "Level II maintenance" award.

Mother also argues that in determining her net monthly income for maintenance purposes, the district court should have applied a 38% tax rate to her gross monthly income, rather than the 35% rate that the district court used. She argues that if the court had determined her net income by reducing her gross income by the higher rate, she would not have sufficient income to pay regular maintenance, and thus the maintenance would have to be reduced accordingly.

Any error in applying a tax rate of 35% to determine mother's net monthly income for maintenance purposes was harmless. The 35% of mother's $12,500 gross monthly income amounts to $8,125. If the court had instead determined her net monthly income using the 38% tax rate, her net monthly income would be $7,750. Mother's reasonable monthly expenses of $4,441, maintenance obligation of $1,000, and child support of $487 add up to $5,928, which does not exceed her net monthly income. Further, since the monthly cap on income for child support purposes was $5,635, a reduction of her net income to $7,750 would not reduce her child support obligation. Thus, any error in determining appellant's net income would not reduce her maintenance obligation.

Finally, mother argues that the district court abused its discretion in calculating father's expenses in light of the higher standard of living the parties had enjoyed in the last four years of their 18-year marriage. We conclude that the district court, having heard testimony of the parties' standard of living throughout their marriage, did not abuse its discretion in determining the parties' standard of living for maintenance purposes.

 5. Attorney Fees

We review a district court's decision to award attorney fees under an abuse of discretion standard. White v. White, 521 N.W.2d 874, 880 (Minn. App. 1994).

The trial court shall award attorney fees when it finds that an award is necessary for a party to assert his or her rights in an action, that the payor has the financial means to pay the fees, and that the payee lacks the means to pay the fees. Minn. Stat. § 518.14, subd. 1 (1996). The trial court may also, in its discretion, award additional fees, costs, and disbursements against a party who unreasonably contributes to the length or expense of the proceeding. Id.

Here, the district court ordered mother to pay half of father's attorney fees. Mother contends that the district court abused its discretion by failing to consider father's "Level II maintenance" payments in determining father's ability to pay and by attributing an erroneous level of income to her. We have already addressed mother's income in section 2. The parties intended the "Level II maintenance" payments to be part of the property division, separate from income, because they were used to equalize the property division that allowed mother to keep both the business and the marital homestead. Father is not required to liquidate the "Level II" payments to pay attorney fees. See Karg v. Karg, 418 N.W.2d 198, 202 (Minn. App. 1988) (award of attorney fees appropriate where payee would have had to liquidate part of property award to pay fees and payor had substantially higher income). We conclude that the district court did not abuse its discretion in ordering mother to pay half of father's attorney fees.

 6. New Trial

We review a district court's decision whether to grant a new trial under a clear abuse of discretion standard. Halla Nursery, Inc., v. Baumann-Furrie & Co., 454 N.W.2d 905, 910 (Minn. 1990). We do not reverse a denial of a new trial motion upon a mere showing that it might properly have been granted, but rather, we reverse only where the denial violated a clear legal right or constituted a manifest abuse of judicial discretion. Peller v. Harris, 464 N.W.2d 590, 593 (Minn. App. 1991).

A trial court may grant a new trial for "[m]aterial evidence newly discovered, which with reasonable diligence could not have been found and produced at trial." Minn. R. Civ. P. 59.01(d). The general rule is that a new trial will not be granted unless the newly discovered evidence is so important that it will probably produce a different result on retrial. Peller, 464 N.W.2d at 593.

Mother argues that discovery of records indicating that father underwent alcohol abuse treatment in 1981 entitles her to a new trial, and that the district court abused its discretion in failing to grant it. She asserts that this new evidence would have cast doubt on father's general credibility and on the integrity of the custody evaluations that assumed father did not abuse alcohol. Mother claims that a new trial would also demonstrate that father currently is at increased risk for alcohol abuse.

On this record we cannot say that evidence that father underwent alcohol abuse treatment 17 years ago would be so important that it would produce a different result. Both parties testified at length in the ten-day bench trial held intermittently from October 30, 1996, to April 1, 1997. The district court heard abundant evidence to evaluate the credibility of the parties. We conclude that the district court did not abuse its discretion in denying mother's new trial motion.

  Affirmed as modified.

[1] This court reiterates that the Hortis/Valento formula provides the proper method for determining child support in accordance with the child support guidelines where a court orders joint physical custody. Broas presents the formula using columns of figures, and should be followed to avoid miscalculations. 472 N.W.2d at 671.