I wish HF offered (or STILL offered, thought they had one..) two-stage bottle jacks like this one from Northern Tool
Much more expensive, but can help get you from Too Low to High Enough.
I'm blessed to have a 12-Ton Walker Made-in-USA jack that must be 50 years old. But when it needs repair it'll probably be scrapped and replaced with a HF.
These bottle jacks are a huge bucket of tradeoffs. The higher the capacity, the EASIER they lift the load. Also a steadier footprint and a higher lift. IF it'll fit under the coach, which is why I'd not suggest a 20-ton.
I also have 2-, 4,- 6-, and 10-ton bottle jacks. The 4-ton will lift one corner of the rear of the 31-footer. IF I can position the handle and work into a position where I can force it down with both hands. The 12-ton's a one-hander doing the same thing.