So...I will try the jack method. I don't think it'll be much of an issue. I tried manually lifting a post and I could start it moving without much effort, say 50 pounds of force or so. I don't need to lift much, just above the surface of the foam, slide a block in, set down.
Did you try lifting since it’s been totally full? The legs are reasonably easy to lift and move when it’s only 1/4 or 1/2 way full, but by the time it’s completely full I think there’s at least a few hundred pounds on each leg.
Good luck in any case