I love my B cup forms. I might go slightly larger, maybe just a C cup. But no bigger.
Which is hilarious as both my practice wife and the keeper are very large chested. The keeper's 36GG. Colour me happy with both sets of boobs in my life. 😀
As to why, well they're pretty handy if you're aiming for full femme presentation. But me, I simply like the way they fill out my clothes. Nuff said.