[brucepick]

From what I've seen in the posts here, the big gains in pickup truck aero are in dealing with the air flow from the cab roof back to the tailgate.

If you can get by without the current cap, you could

- - Easy route: cover the bed with plywood sheeting or similar. Make the panels 3-1/2 feet front-to-rear. So you can remove them and lay them in the bed when hauling something taller.

- - More thorough route: Build a cap that tapers down towards the rear. Search this Aerodynamics forum for discussions on - "pickup cap", "aero pickup", "truck". Or just scroll down through.

Cleaning up the aero underneath is also worthwhile. Working under a truck is way easier than wiggling around under a Civic up on jack stands. Count your blessings!