Kind of funny you ask. When we first got our RV, the advice I read was to buy a set of scissor jacks and use them under the rear frame when parked in camp. Some folks even soldered them to the frame and used a drill and bit that fits the crank to raise and lower them more easily.
I bought a set and brought them along and used them a time or two, but they were too much trouble to set up and take down and we don't mind the motion inside our small C. Rocking is most noticeable for us when someone is using the stairs to get in the door which is in the rear of our rig. Just walking around inside does not create enough motion to bother us.
Try nothing and if you can't get used to the parked motion of your rig, you can buy the scissor jacks pretty reasonably.
