I would like to install a swim ladder on the transom of my 1974 O day 20. The transom is hollow fiberglass and I am not sure I can get back into the area to install any plywood backing. Does anyone have any ideas on how I could safely install the ladder so that I don't rip a hole in the transom climbing on the ladder?I have thought of drilling both the transom and the cockpit liner and installing the wood backing in the cockpit but I am not sure this would work. I wish i could inject structural foam between the two fiberglass layers. I have looked at Great Stuff foam insulation sold in cans but i don't think it would be strong enough. Wish they sold structural foam in cans.