My fender lip sticks far enough out to clear the tire with just a flat piece of cardboard so this was really easy. I used two layers of corrugated for extra strength and then painted them for water resistance/looks. White duct tape keeps the cardboard proto low-profile. Just have to devise a good quick-release system and make a set out of metal. I did these and the bumper fill at the same time so I can't say how much each one helps, but my avg mpg display is reading high 28's on this tank so far where it usually reads low 27's. Oh yeah, and she pulls harder on the highway too ;)