Vassar specifically looks at the rigor of senior year- you don’t want it to be less than junior year. Double APs is NOT going to be what puts him over the line there. Agree with @MYOS1634 that the basic 5 will be fine. Strong marks and ECs that make sense for what his story is will matter much more.
Vassar is where the D2 I mentioned above ended up- with no science APs at all (4 Senior year: Calc BC, Lit and double history- US + Euro). She is now a physics major planning to do PhD apps this fall. I know students from her year (and her sisters years) at Emory and WashU, all of whom had the basic 5, with an average of 4-6 APs (combined) over junior and senior year / none had a double core science.