See attached.
AirTabs work best about 3-6" from the tailing edge. Put the tabs on 4" centers. Any trailing surface with an angle greater than 30 degrees works best with AirTabs
I have these on my F250, not sure how well they work with that headache rack in the way, but I'm still pulling down 27mpg on the freeway with no load.
AirTabs can be sprayed to match the color of your vehicle.
I have two additional AirTabs ahead of the rear wheel arches to keep pockets of turbulence from forming there. I have additional trailing edge AirTabs ahead of the tail lights on the truck as well.