I don't think that BBW and perky really go together. If someone likes someone larger, they have to expect things to sag. I personally think saggy is sexier than perky anyway.
Well, naturally the bigger breasts get, the more they will droop. It's not a bad thing. You will never see natural, huge tits that are perky. You can't defy physics.
Virtually the exact same group of guys who only like thin girls with bleached hair will make a big deal about the saggyness of your boobs.
Virtually the exact same group of guys who adore lovely fat and thick BBW's will not care one big about your boobs sagging. In fact, we'll probably like it!