A lot of talk has been done about using a leveling system (like Bigfoot) and lifting tires off the ground. The rear tires should not clear the ground for 2 major reasons, parking brake is on the back wheels and the air bags are pushing in both directions. For the rear tire not to be on the ground the air bag is stretched out pushing the rear tire down till the suspension will not allow any more movement. Might not be recommended for the air bag suspension unit to be stretched out that far.
I still believe it does no harm to have front tire or tires off the ground. And for this reason; as soon as the level jack touches the ground and raises the vehicle even 1 inch it is starting lift all the sprung weight. That would include everything except tire, springs, shocks, brake, and axle. All the weight of the motorhome, which includes the total mass of everything (frame, engine, cab, motorhome, and all cargo) above the suspension, is already being lifted as soon as any correction is made in leveling.
It just looks scary with a front tire off the ground. Once the sprung weight is lifted correctly and held by the jacks it hardly makes any difference the height. But it would sure make sense to use good sturdy blocks under a leveling jack so it would not have to extend farther then necessary. So if that level lot has all ready been taken, it is time for the leveling jacks to live up to their name.