[tartuffe]

Why will you need only one layer of ply on your transom? Are you still extending your sringers into the bracket? I would hold off on doing anything with that transom door until you are in the final stages of your restoration. Really if your going to cut your splash well out then enclose all your transom except for a 20" width and have the bottom of the passage 25" above your keel and don't worry with a door.