are these plastics panels, like next to the rear passenger in an a body? if so I'm not sure that you want to use j/b weld, at least not the metal epoxy (i'm not sure if j/b has plastic epoxy??). If they are plastic try to find a good 2 part plastic epoxy. I've made heater box repairs with Maxim plastic repair system which is a super fast urethane 2 part. I was able to fill a hole, sand it, drill it etc, with phenomenal strength. best of all it's black and paintable.Is it possible to repair side panels that are missing pieces? I don't have an old panel otherwise I'd splice into the damaged area. Would an epoxy like JB Weld work?