Military/Divorce Question.?

My husband is active duty army. We are divorcing and trying to figure out custody. I have no objections to staying at this duty station for the remainder of his enlistment contract. I want to do a 50/50 custody arrangement where we split down the middle ALL custody and expenses.. He is telling me that in order for him to retain off-post housing, it needs to be 51/49 (meaning he has more custody than me). Is this true?