I bought a 40 year old aluminum sale boat and the two pieces of wood on it are rotted out. The top of the centerboard well was oak, and I am replacing that with a drab piece of goncalos alves that happens to be just the right size.
The transom is aluminum, but the rudder mount was backed up with a piece of plywood. It is only about 14x18 and hate to buy a piece of marine ply for that. I have a piece of baltic birch. If I coat it with penetrating epoxy and paint it, would it be durable enough? I expect it will get wet frequently. I suppose it would be easy enough to replace if it doesn't hold up.

I could glue up the GA also, but the stuff I have is 3" wide, so it would take 5 pieces. (I bought a big pile of it for almost nothing a few years ago, but it is all short and narrow...)

What would you recommend?