I have definitely been toying with just an rv type air deflector mounted to the headache rack.
It might help some when i havea building on the truck. My other thought is that i might be able to somehow use 2 of them together to have a larger deflection area. Mounting a large deflector like on a big rig would be a great idea, especially if i can find one that would fit with minimum modifications. But what would the results be for empty running?
Another thought is running a deflector on each side of the headache rack for the sides.