boobs have to be at least d for me, c is just too small to fit it in the valley formed by the pressed breasts. Sadly I've only ever done it with three women so I haven't been able to prove if pleasure increases with breast size.
here's one for you: thigh fucking
I have a thing for thick girls so it works, my ex was on her period and I didn't have a condom so she just lubed up her thighs and told me to pound away hahaha, didn't really work though but it felt good.
Titty fucking is alright. My favorite titty related activity is to put a greased up hot dog in between them and have her squeeze them together til it pops out, and then try to catch it in my stretched open asshole from across the room.