Divorced 7 years ago, no kids, both worked so it was a straight 50% split down the middle for me. Add in kids and the guy gets FARKED over hard 99% of the time.

80% is high, but i know a couple guys who were financially ruined (ie lost almost everything AND had to pay well over 50% of their continuing income on child support/alimony) so as others have said get your mate to find a good lawyer.