[freebeard]

Most of the van conversions that rely on Type II sheet metal are too wide in the back. This fiberglass clip has, as I calculate, a perfect extension of the body contour. It could be further optimized—fender skirts ... hitch mounted perforated base plate ... plasma trip strips ....

The guy that runs BGW knows that it gets better gas mileage but he doesn't know how much. aerohead, what would your calibrated eyeball say is the Cd? About 0.30? That would translate to 5% gas mileage.

Replace the stock hatch (which really restricts engine access, needs an electric conversion) with V-shaped side-hinged double doors. And the air intake vents with an intake in a V-shaped ducktail spoiler. Boom, instant full boat tail — [Edit:0.25].