I agree, hard to talk about things you can not see! I built the Guillemot and the slight upturn of the bow and stern tends to straighten some when you remove them from the form, thus the misfit at the ends. I used an inner stem and left the end on from the hull which protruded into the cavitiy of the deck, this help me align the ends. When I taped the both ends down tight the fit was perfect, but I too had about a 1\4" misfit at the cockpit area, the hull was narrow.

I cut stick braces using forms 6, 8, 11, 13 for samples and forced them down to spread the hull to exactly match the deck. Then a real tight taping held it inplace, removed the braces and taped the inside. Good luck on yours!