Having built several CA Doubles, I know what you mean. I would plane down the hull and/or deck to remove all bead and cove to get a better fit. You will have to make several dry runs. The only down side to this is if you have an accent strip at sheer line you plane down and thin in one area but not others andt the difference may become evident to others. After you plane down to fit, take a two by four wider than the boat and wrap and staple some 80 grit sandpaper to the wide side. Take the 2 by 4 and run it across the hull and deck at sheer. This way you will get a flat surface between sides and a great fit with very little gaps.