Quick question about transoms.

I've been given a 14'48" that needs a transom. (Just the wood, the metal is fine) I've looked at a few pics, and it looks like I don't have to cover the entire transom with wood, as long as I get about 95% covered. Is that acceptable?

I'm mainly worried about the corners. I fully intend for the wood to cover top to bottom, and side to side. It's only going to see a 20HP mariner, so there's not going to be much stress put on it.

Thanks in advance!

When I got my 1436 it was missing the wood. I could tell what was there and replaced it with the same size. 2 layers of 1/2" plywood measuring 12"x48" I then added a 1"x6"x48" oak board and glued and screwed it all together. I'm running a 25 hp mariner.