[Big Dave]

I can see the shape you are looking for, and I like it.

Next order of business is two or three intermediate supports for the sides.

Have you thought of this? Build essentially a topless top and use a commercially avaiable rollup toneau cover as your "roof." This way you get the aero advantage and the flexibilty a pickup needs.

Your wood frame would be the perfect support for a mold to make this baby out of fiberglass.