Use same screws, tip get you a self tapping screw same size as mounting screws. Use it to make each hole then install your mounting screws with a small dab of JBWeld on each screw. It will help seal if there is any wood involved and will anchor the screws. If drilling holes in gelcoat put a double layer of duct tape down and drill through it. Helps keep it from splintering. Mounting finders on anything thin make you a aluminum backing plate to reinforce. Or at least use as large a body washer as you can.