The plywood arrived. I had an hour to spare so I couldn't waste it. First sheet marked out with the boat sides and outer transom, all in 5.5mm plywood, which looks quite good. It has been stored flat so there are no nasty curves in it. I have marked the stem, which is just a square section batten. The sides meet at 90 degrees at the bow. As I said this should be a very simple boat to build. I am sure I can prove that wrong.
I am building the transom in two layers, a full sized one in 5.5mm and an inner one in 9mm, 5.5mm narrower. That will give me a recess to glue the sides into before I fillet the joint. You can just about see that I got the initial drafting completely wrong. Measure twice and cut once as they say. First diversion from plan. I have added a 50mm curved top to the transom. It will look enough of a box as it is. I may put a sculling notch in it. Or not.