To deal with the sagging, you add C-flex. C-flex is thin glass 'rod' stitched together by E glass. The rod provided the stiffness to spend between the forms. The whole thing than is saturated with polyester or epoxy (notice epoxy has no advantage over poly and poly is cheaper and stiffer). More layers of fibreglass ( usually alternate layers of mat and cloth ) are added to provide the thickness. The whole shell is than pop off the forms and more layers are added to the inside with the last being 3 oz for smoothness. You do not need to use wood in this kind of construction ( except for the forms.)
C-flex is usually used for one of small fiberglass boat construction as it does not require a plug or full female mold--$$$. Nick's internal form system works well withn this kind of construction.
Hope this will help.
Good luck.

: He also said the fiberglass 'scalloped' between the stringers, I guess the
: cloth just sagging from weight of epoxy in between. It would have a better
: appearance if you had a nice tight covering but I don't know how you could
: stretch it and keep it tight until the epoxy sets up. Probably not much of
: a performance issue. Any thoughts? Would kevlar cloth stretch tight? Could
: you pull it and tack it with hot glue or something?