Zjorz, I want to thank you for asking the correct question: Given a fixed band size, who has the biggest boobs? A girl with a 32D is going to be a lot bigger proportionately than a 36D.
And I agree that with a 32L or M, balance becomes a problem. Maybe she should lie down. Maybe I should join her.
Indeed. Thank goodness, I was about to come into this thread and make fun of you. You phrased it wonderfully.
I'd say that maybe an M or so is the highest reasonable size. Some may be larger, but after a certain point the detrimental health issues (she'll snap in half!

) outweight the benefits.
Frankly, the 32L girls baffle me. I'm a 38H/I and I have no sense of balance most of the time. People tease me when I randomly wobble and try to regain my center of gravity. And I've got booty to cancel it out. Those girls are super slender except for their chests. They must topple over all the time!