I have a busted transom on my 14' trihull. This weekend i'll begin cutting out the entire transom and going shopping for new plywood. I already have some outdoor 3/4 and i was thinking of getting some 1/2 inch to sandwich with it to keep the weight down instead of 2 pieces of 3/4. My question is if this will be sufficient? Also, can i use 5200 to seal the the two to together then i will glass with biaxial and poly over everything? Am i heading in the right direction?