Can't edit player.img

[Dimwit]

i downloaded a couple of skins for the player.img and the instructions say to use the ultimate editor and open player.img, click on the file click replace and then click on the edited file. well, i wanted to make my own, so i extracted a jacket txd from the player.img using the ultimate editor and i opened it up in the txd workshop sa beta program, i edit the jacket file and then go back into the ultimate editor to replace the file. and when i go in the game to buy the jacket, it freezes on me. i know that the txd editor works fine because i editted some textures in the particle.txd and it works just fine. so does anyone know what i'm doing wrong? why can they get it to work and not me? are only certain files in the player.img editable?