[tartuffe]

I used 2 layers of 3/4" marine ply.

First layer: In order to get that bend I cut 2 score lines about 3/8" deep at an angle, makes conforming to the hull much easier.

The score lines are on the side that faces the bow, not the side that will attach to the existing transom skin If you look closely at the transom you will see how the curve in the transom comes up at about a 60 degree angle on both sides about a foot on either side of the drain plug hole. Your score lines should follow that line.

I hope this makes sense, have plenty of clamps available.

Do a couple of test fits and try a dry clamping run.

When you are ready to do it for real, trowel a heavy layer of thickened resin on the existing transom skin and trowel a layer on the ply that will touch the transom skin and sandwich the thickened resin to the skin, clamp it and leave it overnight.

Second layer doesn't need score lines, again put thickened resin on layer you already clamped the prior night as well as the layer you are about to place. Sandwich together and clamp, lots of clamps.

I made the mistake once spreading a heavy layer of unthickened resin on the wood prior to troweling out the resin, the thickened resin won't stick if you do that and will ooze off the wood. You can use a very light layer of unthickened resin but don't get carried away.