I'm looking to strengthen, and help hold the curvature I want in my hood and engine cover. I know a number of folks have done this with various things that they then over-laminate into place with fiberglass cloth. I think so far I have seen balsa (similar to the old 914-6), PVC, and aluminum.

I'm thinking about using carbon fiber. A fairly inexpensive option would be to use solid carbon fiber rod. It's available in many diameters and not too expensive (~$25 for a 3/8" diameter, 4' long piece). The only problem for me is that, without several diameters of carbon fiber rods on-hand, it is difficult for me to determine which diameter I should go with. It would obviously need to be flexible enough to conform to the slight bowed shape I would need, yet stiff enough to provide rigidity once glued in place.

Right now I'm guessing that 3/8" or 1/2" diameter solid rod would be what I'm after, but thought I'd pose this question to everyone else to get input. Maybe there are some die-hard composite gurus on here?