Flattening transom skin before installing core.

[captsuperfly]

I'm rehabbing a 23 Seacraft and am getting ready to install a new transom. It's an I/O to Bracketed Outboard conversion. Old core is removed, previous holes are filled with epoxy/1708 layers and flush with the inside of the skin.

With the old core removed, the skin itself has a little bow across the middle. It's easy to push back into shape. I'm about to lay 3-4 4 layers of 1708 across the entire inside skin before setting my Coosa and I don't want to reenforce the bow as I lay the new glass, I want to get it flat.

Two choices I'm considering:

1) I have a 1/2 inch ply rough transom template that I can place along the outside of the transom to brace it like a giant, wooden, transom shaped washer. I'd put 2X4's across it to keep it true and drill through the skin and use small bolts pull the skin against the plywood and 2X4s. That will get it flat. Then I'd glass over the screws with the layers of 1708 and cut out the screws and close the holes after installing the Coosa.

Downside is I hate extra holes and I worry about the 1708 laying flat against the screw heads -I might create a bubble around them but I guess I'd just grind that out too.

2) Instead of drilling holes, I screw the plywood to the 2X4s (which would extend past the sides of the boat. I can through bolt eyes on the 2X4s and use ratchet straps to pull the whole thing tight the transom.
Upside is no holes. Downside is that I can see getting the whole thing to pull tight being difficult.

Any better ideas, I'm all for hearing them.

​​​​​​​thanks!