Actually, Kevlar is stiffer then glass, and is really a good material if you want some flex and good stiffness, thats why its used in bullet proof vests, it's stiff, yet flexible. it can be flexed but it takes a lot of pressure todo this.

another Idea I had was to do two sets of composite ribs... one set on the inide made of kevlar, and one on the outside made of carbon fibre. Basically the same idea as the black gold layup of the Bell Canoe Works composit boats. www.bellcanoe.com if you aren't familiar. It's by far the nicest layup of any production boats out there. The reason for the kev inside and carbon outside is that carbon is incredably good when being compressed, and kev is best when being expanded, so when the boat hits the water, it produces a VERY stiff combination.

I just finnished putting glass ribs on my model, I'm going to try and get pics of it up here on saturday. it looks pretty nifty, I made a mini set of forms n everything.