: . . . But then on each
: side I have a gap starting small then expanding up yo 3/16" and back
: down again over an area about 3 feet long. . .

If you can so easily identify the area of the problem, and measure it, get a scrap strip and force them into the area which is pulled in. measure the beam at that point and make your strip (or temporary thwart) 3/16 longer that what you measure, if it is pulling in 3/16 inch. If it is pulling in 3/16 on both sides of the boat at this point, then your thwart will be 3/8th inches longer than whatever you measure it to be. That will force out the area, and hopefully make hull match deck.

To be doubly sure of a match, make two temporary thwarts out of your scrap strips, and make them exactly the same length. Then place them exactly the same distance from the bow (or stern). Since your hull should be made of strips which are uniformly thick, when you have used these equal-length thwarts inside the boat they will force the outside to be exactly the same at that point--and things should come together perfectly.

If the temporary thwarts won;t stay in place by themselves, use a drop of hotmelt glue on the side of the thwart closes to the center of the boat. You can break the thwarts easily once the deck and hull are attached. Flex them and they should pull off the blobs of glue as they come out.

Hope this helps

PGJ