I just spent upwards of 20 minutes trying to place a flower on Leixia's shoulder in a custom costume. The problem I ran into (and never really got around), is that Leixia's breast jiggle during her fighting stance doesn't appear to affect only her breasts: the character mesh of her neck and shoulders seems to be affected as well.
Basically, I wasn't able to successfully place a flower on the front of her shoulder in such a way that, during her battle animation, it didn't disappear inside her shoulder, and then reappear repeatedly as she bounces from side to side.
Is there any way to minimize the effects of character warping when creating custom costumes, short of equipping 'solid armor' to the character as outlined here? Some of these warping effects make it really difficult to avoid strange behaviour when placing accessories on custom characters.