I have many screws coming loose. I have replaced some with fasteners that look right, but they quickly rust. Does anyone know where to get good replacements for a good price? I also don't know why, but many screws are coming loose under a vinyl trim that runs the length of the camper, about 18 inches from the bottom of the camper. When I tighten them, they do not snug up like they should. What is behind the siding? Will replacing with a larger screw solve the problem or create more problems in the long run? Any insight would be greatly appreciated! Thanks ahead of time.