I'm working on a race car project. I'm repairing some fiberglass panels and I need to smooth out the rough areas. Best way I know how is to use body filler. Question is; which one? Since its on removable body panels, they need to be light weight and flexible so it doesn't crack. Here is a pic of where I'm at.... This is my first fiberglass work. Let me know how I'm doing and any advice would be appreciated....