As pictured a diffuser Phil Knox helped me make for my 4 Runner for towing Apex. It was attached to the rails on the roof of the 4 Runner. It is made from the rear lift gate of a Toyota Highlander. At the bottom it is 8 inched narrower then the bed of the truck. At the top it is 74 inches off the ground. So in theory it should aim the air at the top of the trailer but is only about 2/3rds the width of the trailer. I may experiment with a piano hinge to allow the partial bed cover to lift up in the center. It would need side panels though which this lacks. I like the radius edges of the home made diffuser though.
