I have the Flex-a-lite fan setup... I like it so far, but have been pulling largely unloaded. I just bought a 30 ft Gearbox 5th wheel that weighs 14k lbs fully loaded, 9k lbs empty. I took it out this weekend (earound 80 degrees, trailer empty, a/c on)to see what it'd do up a 6% grade at 65...