What do you guys think about them They vary in price quite a bit, cap isnt really an option, but tossing it in there for comparison. Fuel economy- Do these make a difference? I have heard they are good for a few MPG's. I tried driving with the tailgate down for a good stretch of road. Felt pretty good, seemed to have added 1 or so MPG. My question is, with a tonnau cover, are you loosing your ability to strap stuff down? do they make ones with loops or strap hooks?