A CF bonnet will require a mould every bit as expensive as that for GRP. For strength, carbon fibre construction is done by laying up the epoxy and CF, bagging the whole thing, pumping out all the air and then baking in a high temperature oven. If high strength is needed then another outer skin, bag or shell is required so that the article being molded can be placed under pressure. Things like carbon fibre race car tubs, wings etc etc are done in an 'autoclave' with a complete mould set covering every surface and under VERY high pressure as well as high temperature. Not withstanding all that, I must admit I've been toying with the idea of a ferro-concrete mould of the bonnet and then doing a bagged & baked ECF replica. Bloody expensive and time consuming though!