I know these things aren't exactly fuel efficient or bought for that purpose but what sort of mileage are you guys getting with the camper on and is your rig gas or diesel?
Just for comparing old vs new truck technology . My 454/460 GM and Ford DRWs in the '70s got 4-6 mpg carrying a 10' 6" truck camper at 55 mph (national speed limit). Hell those old gazz hoggs got 8-10 mpg just sittin' or running empty.