I agree with what FloridaGirl said about how rushees who go to the maximum number of parties should get a bid--with one caveat. Somebody in PH should monitor the sororities to make sure that the sororities haven't asked back more than they should have. Without that, we all know of some groups on our individual campuses who would cheat by saying, "Oh, whoops, we asked back 10 more girls than we should have and whoops! I guess we'll have to take 10 more than quota!"
Betcha that all you ladies can name the exact groups that would try to pull that on your campus.