Short answer:

If you want a girl with unusually large breasts, conforming clothing is not the way to clothe her.

Two things to consider:

First, conforming clothing is designed to follow the movements of the bones in the base figure. The actual shape of the clothing is determined by morphs put into the clothing figure, not the shape of the base figure. Breast morphs especially are problematic, because (for example) a girl with very large breasts will have a very deep inframammary fold under her breast mass, while the tee shirt that goes over it has no reason to follow those curves in reality. Due to the way the shirt is modelled (i.e. to follow the curves of her less endowed sisters) it tries to cling to every curve and winds up folded against itself. Conforming bras especially do not work well for girls with NBS (and other enhanced) breast morphs.

Dynamic clothing takes care of all of these issues automatically. It takes gravity and cloth stiffness into account and dresses your character in a far more realistic manner. The secret in using it is to start with the breasts at zero morph in frame one and let the cloth expand with the bust to the desired effect in frame 30. There are a number of VERY good dynamic clothing items here, including an outstanding set of underwear that takes care of these busty lasses quite well. There are also a large number of free dynamic articles (of widely varying quality) that you can experiment with if you like.

I own a lot of both kinds of clothing, but when one of Dolly Parton's cousins is in one of my renders, she ALWAYS wears dynamic clothing. It just makes life a heck of a lot simpler.

My $.02. Your milage may vary.