I made the fairing by using 1/4" foam and using 2 part foam as adhesive to hold the various parts together. To get the 3 d shape near the front of the fairing I cut pie shaped wedges and pulled them together while gluing behind them with the foam. Just gave those areas a bit of shaping with 36 grit sand paper.
When I had achieved the shape that I wanted, I covered it with a single layer of carbon fiber and painted on epoxy.
Although aesthetically pleasing it was too long and didn't work any better than the little fairing I had prior.
The shape was determined by the flex in the material.
My mini van nose cover and wheel spats were basically the result of fabric stretched over areas and then composite was laid up over the sails created. Much faster than carving and sanding. If I were to do it again I would clear window film plastic and build the reinforcement on that. If you are interested could post them again.