Thanks for the info. I might consider just adding some additional (manual) jacks before this option. Price is not that much different.
On my old camper I had some jack-stand style jacks that I used at the axles to help take out the suspension movement. I think they are too short for this camper though.
The other thing I like about the manual jacks is the ability to influence the balance of the trailer. Earlier this summer I had it all nice and level and then when I put out the slides the weight shifted enough to put that side a little low (I think the tires settled into the ground a bit too, not helping) and there is nothing you can do to influence that, short of putting everything back in, attaching it to the truck, moving forward, putting down blocks, backing back up, and then setting everything up again. Too much hassle so I just lived with a slightly off-level camper for the weekend.
anyway - thanks for the info. If these were cheap and easy I would jump on them. But I will perhaps just add another set of jacks.