As long as the upper abdomen slightly raises the breasts, serratus is visible from side/back and midriff is showing, all is good in my book.
I think there is such a thing as too big. There is no defined limit like anything over blank centimters/blank-cup is too big. It's all about does the size of the chest fit the rest of the girl's body. For example Lucchini is a small girl and would look ridiculous with huge tits but Shirley's breasts are proportional to the rest of her body.
did you really need to ask
only people willing to say no are the closet shitters that leave 2-3 point reviews about a show due to fanservice