Had not thought about the fabric in the corners, that is something to play within the shop this week on a mock-up and see how hard it will be. I was thinking about just stapling the skin in place inside the opening. Trimming it with a varnished piece around the openings. These would be screwed in place to hide the staples and fabric edges. Square corners would be easier to trim out. Your right about the fabric, I hadn't thought of that. I have some 12 oz scraps and will have to see what I can do with it.

I have seen this a lot of older sail boats and a few of the old Fuselage style boat plans from Popular Mechanics and the like that use a coaming like this. With the large opening I want to use it as part of the structure. It should stiffen up the boat and keep down any racking of the frame.

Since this is similar to a decked canoe, I have thought about just one one large opening instead of the two. I figure this is stronger and a little stiffer. Plus I like the idea of being able to sit on the deck to fly fish. But I think I will look at just making the opening symmetrical and putting a thwart and backrest combo like Thomas Hill does in his canoes. Sit the cooler right behind me and it would easier to sit on it. Thanks, never hurts to look at other options!