I used a 2×10 on another aluminum, wolverine, that was originally 15". Pretty much how u explained. I was told 2 or 3 pieces of plywood was stronger and could flex with out breaking. Im probably going to do what every is cheapest and easiest. Thanks for ur input:)
Just about the start a restoration on a boat that has been in my family since 67. I have been using since 2000 with a 25hp tiller. Bought a 30hp with consule, controls, steering and electric start:)