Leveling

We just purchased our used 30' last year. So far been using the lego blocks with some extra wood planks.

Have been looking into putting Lippert scissor jacks on it, but the rep said that it would not work. That they could only be used for stabilizing. Doesn't make sense to me. Each jack can lift 5000 pounds. Why would you need that kind of lift just to stabilize? Can anyone explain it to a newbie?