^Agree, I've got big boobs and no ribcage to speak of (it's the same measure as my waist), but because of that I'm still on the smaller side for measurements, and the small brands even fit me better. Overall measurements are more important than bra size.
Button-up blouses are tougher though, always be wary of them; I have a Mary Magdalene blouse where the MAX bust measurement is 82cm (not kidding, but it's old, and I think they make larger sizes now). I have to wear a camisole bra to flatten myself out a bit to wear it comfortably. If I do that, it fits like a glove. My Innocent World (size M) blouse, however, is SUPER roomy in the chest, and still fitted at the waist! Very nice fit for more busty girls.
Babydoll/"bag-shaped" dresses look fine on me, they just make me look really... really flat-chested. But that's okay because they're supposed to be relatively shapeless anyway.
Fanime 2013 Lineup:
Minako Arisato (Persona 3 Portable)
"Yuko" Narukami (Persona 4)
I have a tumblr too!