I store my camper on a steel dolly (pic below) inside my warehouse… mostly because it is convenient, stable, and it gives me the ability to roll it into the corner of the bldg where it is out of the way. I also take into account that I live in earthquake country and I'm not 100% certain that the TC's jack's alone will be able to withstand the shaking when "the big one" hits. The dolly/stand (in conjunction with the jacks) is strong enough to take whatever Mother nature throws at it… So for me it's about convenience and cheap insurance against damage.
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In addition, owner's manual for my Alpenlite includes the following statement:
"Do not leave the camper standing free in its four jacks. Support the camper and particularly the floor with blocks located towards the outside (so the bottom of the vertical wings are supported as well as the floor) or by using sawhorses which spread the load from side to side."
Cheers
-Mark