Newton and counter-reaction is naio's issue. I am a member of his club.
Naio your jack leveling connecting point rises as the jack rises. This makes it hard to control counte-torque. Harbor Fright used to sell an electric 12-volt scissors jack. Using blocks I use that jack to raise each corner of the rig then when it gets high enough I use the original jack alongside to make it stay up. Sometimes thus has to be done in a couple of stages. Raise, set the original jack to keep the rig up, place a block under the electric jack raise some more then the original jack is extended to keep things up. Move the electric jack to another corner. It's fast and by god a lot easier on hands and wrists. I could not afford electric lifts in a million years.
GOOGLE 12-volt scissor jack. You'll need enough power cord to reach the furthest point.
Hope this helps.
