New to making custom skins

[LYBHYDRA]

I'm VERY new to making custom skins in mxsim. I've been making lots of stuff on mxbikes but their way to make custom stuff is much easier. I recently FINALLY figured out how to get my own custom skins into the game, but when i do, this grey waistband looking thing shows up that im 95% sure isnt supposed to. Im assuming its something with the jm file i got from the boots that are astars tech10's from a post in like 2020 i think, but im not sure bc ive never worked with a jm file before. Just need to know if theres a fix for this

[LYBHYDRA]

this is the image:

[i will trade you]

whats your dc i can help

[LYBHYDRA]

whats your dc i can help

HYDRA#2967