Help! Texture after model edit.

Hello guys! I need some help, i want to edit the GK4 bust.emd becouse i have a hole between the bottom of the bust and the top of the pants. When i edit the model of the bust by dragging the bottom points a little bit down, then repack it the alpha texture with black lines is completly wrong. I know here is some tutorial threads but i cant get it work with that. Sry for my bad english  . I hope you guys can help me. Thanks!