We left the dimensions the same, but made several modifications. We did away with the stem lumber, and used 'stich & glue' instead.
Then we moved the chine outside, doing away with the necessity of carefully fitting it on the inside, and having to saw notches for it in the temporary midship frame.
Doing this made the bottom just a little wider amidships. The four feet of the plywood are not quite enough to go all the way to the outside of the chines. It seems to be ok though, and we will cover it with fiberglass cloth.
Since the design did not include flotation, we did away with the seats and instead are fitting the boat with a foreward and an aft compartment. These will be filled with foam and double as seats.