I made four sets of four 2x8s cut into lengths that, when stacked properly, can raise all four rear wheels six inches. I cut 45 degree cuts on one end of each of the boards. I have forgotten the exact lengths, but essentially it was 9, 18, 27 and 36 inches for each set. These could then be used to construct a ramp using one, two, three or four pieces, 0-6 inches high in increments of 1 1/2". I drilled 5/16" holes in the appropriate places in each plank so as to drop a few 1/4 inch carriage bolts to act as pins to keep the boards from slipping on each other when in use.
I then went to Academy and bought two nice bags and put two sets in each bag. I carry these bags in our toad. Why? Because we camp mostly in BLM or NF campgrounds boondocking and some spots that need quite a bit of leveling sometimes.
After using these for a couple of years, they now reside in my shop and have been replaced with four sets of the old tried and true plastic block levelers. I had two sets already and have used them for ten years. So, six sets of ten plastic interlocking orange levelers.
WHY? Because the boards were just too bulky and heavy to carry in the unit and took up too much space in the back of the Jeep. Most times, we needed to level no more than three or four inches and the blocks do that fine. I over engineered!! Boy, the ones I built are nice but they weighed a total of 110 pounds and filled an area 16" by 36" by 12"!! AND, I had to strap them down in the toad in case of an emergency braking situation. The orange blocks weigh half that and take up a lot less room. They don't work as well and are certainly not as sturdy, but they are sure easier to tote and use.
As to hydraulic levelers, they would be real nice but just cost too darn much for my blood. I have never had them, would love to have them, but not for 3 or 4 Large.
Lesson of the story: sometimes less is more and don't over engineer in your retirement years.
Paul