: http://community.webshots.com/album/87983603paidmx

because you have already glued and fixed the edge betw the sides and the bottom without having either consecutive forms or upper panels to restrain the sides, the bending BETWEEN the both of them is affecting the curvature of the bottom locally.

you may glue the lower sheer clamp in place on the bottom/hull, but i would cut away the sides(use a flush cut saw) and only stitch them in place to locate so that no bending is imparted one to the other. put/wire/hotglue in a couple(or a lot) of temporary sections to hold in place and symmetrical and resolve the upper deck.
when all is figured out only then glue in place.

if you don't want to do this, glue in multiple glassed transverse beams across the bottom similar as i suggested below. they will put the stress back in the side panels.