I had to do something similar in a campground once. As long as you are not trying to raise both ends with the stab jacks it's OK. As long as it's choked good it should be safe. Lowering it would require a few sets of blocks to keep raising and lowering the tongue jack till it got near the ground.
I passed on many houses because of driveways like that. I couldn't imagine parking my car in that much of an angle let alone a trailer!
02 Ford Excursion V-10 4.30 gears 5 Star Tuner Y-pipe mod Hellwig sway bar Rear Airbags
Prodigy and Dual Cam
07 Cherokee 32B
Better to have a bad day of camping than a good day at work!