the 2nd thing I like most about sof's is their ease of construction
so I don't like your idea of making a s&g & then destroying it
for the sake of an sof.

(the 1st thing I like about them is the ability to be made as foldables.)

oh, well... you can't please everybody 8-P

anyway, I found something that might help you:

Gerald maroske did something in a similar direction of what you're
saying.

I posted an image with this message but I'm not sure if it's small
enough, so anyway, the link for the image is:

http://elwood.gpi.uni-kiel.de/Kayak/45.jpeg

& the link for his site is:

http://elwood.gpi.uni-kiel.de/Kayak/index.html

he chose to put his "dotted plywood" from the inside of the ribs so it will be
away from the skin. perhaps you should consider putting the plywood on the
outside.

good luck.

Erez