There have been some good solutions provided here for your standard A-frame trailer with a strong frame. Thank you all for the recommendations!
The Hymer Touring GT is a strange beast. The shell has a tubular steel frame "skeleton" that is bolted to a very simple T-shaped trailer. The end result is a short straight tongue (like a boat trailer) and minimal structural strength aft of the axle
. All leveling must be done at the wheels or at the tongue, and the four corner stabilizers are just that--stabilizers, not leveling jacks.
We have used the trailer three times at three separate, well-maintained state parks. I have parked it several times in my driveway and on the street. I have never been able to get it level front-to-back.
I recently came across a bolt-on rack-and-gear or rack-and-pinion trailer jack with semi-removable wheel. It is 22" when extended and 6" when retracted (with wheel attached), and does not swivel. This seems like it would be perfect, since the swivel jack takes up precious space along the tongue. I would plan to modify the wheel with a toggle pin for quickly removing it while in transit, giving me plenty of clearance. The only downside I see is that it will obstruct trunk access while fully retracted, but unlike the drop-type jack it should be fine when extended. Are there any other downsides to using this style of jack on a camping trailer?