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?
2016 Ram 2500HD - 6.4L Hemi gasser - Adventurer 80RB (loaded about 2480 lbs) Georgia to western Canada and back, roughly 8,600 miles Hand calculated (meticulously) for entire distance - 13.8 mpg
This is driving sedately at 60 to 65 mph. On one 170 mile stretch across Montana I got 15 mpg.