Six-Ton, as noted above, is hard to pump when you're under the rear of the coach. We have 2-, 4-, 6-, 10- and 12-ton jacks. The 10 and the 12 are way easier than the 6. 4 is about impossible from under the coach, and 2 of course won't do it.
Remember this, when you lift a "corner" especially in the rear, you're lifting at least 60-70% of the axle's load. Look how wide the coach is, how far you have to get under to clear the inner dual and get on the axle, and how much the opposite side rises as you jack the side you want to lift.