Follow - up ... Sunday I was out at the storage barn where I keep my trailer and where the owner uses these Go-Jack units all the time to move machines, trucks, boats, etc. I asked him what he thought about the feasibility of doing this with a larger, 10,000# unit. He's a mechanical engineer, and he looked at me as if I were a total moron. His answer: of course it will work. His experience also is that you can overload these things quite a bit ... it might shorten the life of their bearings and wheels, but he's never had a catastrophic failure. So - I bet it will work for you also.
Second point: you've got so many followers on this thread, you should just get a case or two of beer and invite folks to come over and pick 'er up and set 'er back down where you want!