Need help with outfit studio

[KuteKatty]

So i'm editing this skirt (Lind's woodland alchemist) to have a shorter but non revealing skirt, while pulling it up to her torso, kinda like a dress skirt, but since the body has physics included it clips, so i try to copy the body bone weights into the skirt, it works as intented, but the middle of the skirt turns into this ugly, squared thing with no physics, what am i doing wrong?
can't get screenshots atm bcs i'm currently fixing a CTD upon opening the game.