The original
Ventura guard was an aluminum channel frame with some
fiberglass roof panels inserted. Worked fine but I would have preferred a flat surface. I have laid up flat
fiberglass panels (but not big ones) by using a plywood surface covered with Formica which got a good coating of car wax as a release agent. Lay down the
fiberglass mat and resin and let it harden, then pop it free from the formica.
One thing I had thought of when I had the
ventura was a bubble type wind deflector as a rock guard, serving two uses. The front the trailer was very flat and caused a lot of drag and I thought that this might help.