I am doing some work on a aluminum boat I bought; however, after removing rusted screws and part of the wood transom, I found that they drilled holes the size of quarters into it (picture attached). Besides welding because I have no experience doing that, what is the proper way to fix it. I plan on using flex paste to fill the hole as well as marine adhesive with an exterior aluminum plate, though I am not confident it will work for the long term.