Thank you all...
I am think of two layers of this with titebond 3...the transom is 1.5" thick
https://www.homedepot.com/p/Cabinet-Grade-Plywood-Panel-Common-23-32-in-x-4-ft-x-8-ft-Actual-0-688-in-x-48-in-x-96-in-1077486/302610611
I just haven't decide to use oil based paint, spar urethane, or...