[wingnut60]

Doesn't the side-side leveling system work much as Glenn described as "getting the wheels off the ground"? As far as raising the trailer itself with some sort of jack under it--doesn't seem too smart to me. Making sure the jacks are always in contact with the frame--making sure they wouldn't slide off the frame--sounds kind of scary. I'll stay with my old-style boards-under-one-side leveling. The leveling system would be the way to go if you can afford it.
I level with boards, set the chocks (both sides, REALLY crank them tight) then unhitch and level front to rear. I usually takes a little more "up" on the kitchen slide side to compensate for the weight of the slide when out.
I also use pads under all jacks to spread weight, to keep the jacks from settling into the ground--have seen many places on asphalt where jacks have pushed into the surface.
My trailer stays very stable when I remember to do all this in setting up.