I live on a large lake and a neighbor and I was toying with the idea of making a ¼ or 1/5 scale Type VII boat to park along our dock. It could be up to 54 feet long and would of course be a several year project. We were going to make a few small scale mock ups by possible using a canoe as a starting point for the hull. Depending on what model canoe you would use it is do able. If you are any good at wood and sheet metal work along with using car body bondo you can add a flat deck on top of the canoe and go from there. You can use large PCP drainage pipe cut in half long ways for the saddle tanks. It’s just a matter of putting it on paper then becoming creative.