[Carl n Susan]

I have always done this unhooked from the truck. But that is because it was a planned task and it was already that way. I would not be afraid to do it while hooked up, say on the side of the road after a blowout, assuming your hitch allows side to side pivots.

One additional detail. The "brain" in the Level Up will not allow you to lift one side to an extreme. And their definition of extreme may not match yours (I know it doesn't match mine). Once one side gets to 1 Degree or so of angle, it stops movement. You then need to raise the opposing side to even it up and then you can continue to raise the first side. This usually only needs to be once when lifting (and of course, the same process when lowering).