This one has been beat to death, but there is a major point that is being missed. I think "dougrainer's" point was misinterpreted. When you drop the air out of a diesel, the suspension basically disappears and the jacks are lifting the frame. Here is the important part....jacks extended 6" are more stable than jacks extended 12"....they just don't wobble as much.
On a gas chassis....the jacks have to extend further to overcome the suspension and stabilize. Even then, they don't completely defeat the suspension which can allow for some bounce. This is a point that was missed when the OP was placing blocks under his coach. He just made the issue worse.
"dougrainer" provides a lot of information on this forum especially when it comes to A/C and refer issues. It's hard to always express things precisely and then others can misinterpret.