You need to use a flexible product. Car Flex is what I used to shave and fill my bumpers and de rib them. you can clamp it, and heat it up a bit to mould it back, them apply teh car flex. It is in a red can, and you mix it with 2-1 parts with hardener. This will give you a flexible and plyable repair that will not crack like fibreglass, or bondo. Do not use fibreglass........
