FWIW, This is what I had and or went thru. Old truck, '03 F250, had flaps attached to fenderwell. I added via cutting another set of flaps and additional 5"-7" of flap to orig flap. Then had a full width rubber flap attached to receiver to further aid in keeping debris off of coach. Worked well and w/o the full width flap, stuff didn't collect on rear portion of fender/under bumper. New truck, '15 F350, did same thing w/ flaps on wheelwells. Full width flap worked w/ old coach. New coach, due to shape of front end by landing legs, the full width flap won't work cuz it will hit the RV when turning. Surprisingly, with just the wheelwell flaps, nothing hits the front of the coach.
