I carry a big plastic bin in the aisle of my Fleet. In contains, among other stuff, a bunch of pieces of 1-inch thick lumber, of various lengths (maybe 12", 18" & 24"), which are used to level the camper. These are sections of 6-inch pressure-treated "deck boards". I stack them up as needed and drive the truck up onto the stacks, first shifting into 4-wheel-low so I can go up in a controlled way. Each board has a hole in the center and I use some 1/4-inch bolts as pins to keep the stacks from shifting. If a stack is really tall and if there is a board left over, I lean it on the end of the stack as a little ramp.
This method requires some trial-and-error, but I've gotten pretty good at estimating the stacks from the level readings. I use a 2-foot bubble level. If I leave a site planning to come back, I leave the stacks of boards in place on the ground, so I don't have to figure it out again.
I haven't had much luck using the airbags for leveling side-to-side. There's just too much interaction between the sides. It's useful for front-to-back, but I use the boards first.
The camper doesn't have to be perfectly level. Head of the bed (front of truck) higher than foot is important. I don't see the need to stabilize the truck; it moves up and down on the springs as we move about inside, but we don't mind.
- Bernard