I am replacing the transom on a 1969 Polarcraft aluminum jon boat. The original wood is 1 1/4 thick plywood. It is 12 inches tall and 63 inches wide at the widest. Everything that I read says to glue together 3/4 marine grade plywood. If I go with plywood, I will need two full sheets, 1/2 inch and 3/4, to get to 1 1/4. Is there any reason why I can't use a solid piece of 5/4 lumber? If so, what kind of wood?