I'll have to report back on impact to range and efficiency. Thinking it should help aerodynamically, but that's probably offset by the added weight. None of that mattered to me, because I wanted the Lightning outfitted the way my 2011 F150 was. I also installed a BedRug on the bed floor, and it has a factory installed spray-in liner. Perfect for dogs that like to go for truck rides.That is the exact route I am looking to go, I would be interested if you notice any impact on freeway efficiency. I would love to see somebody do an efficiency comparison between the Leer and a fastback topper.