This is a brief explanation of some of the forces at work while you are lifting a load with a jack or cylinder. The main line of force is through the center of the plunger. The weight should be distributed as close to this center line as possible. The entire base of the jack or cylinder needs to be on a solid and level surface for a stable lift.
If the load is not centered or the entire face of the plunger saddle does not contact the load, side loading will occur. Side loading creates an unstable setup which may shift or fall. It also damages the jack or cylinder by distorting the wiper seal and bending the plunger. Side loading increases with distance. The further you extend the plunger, the more unstable it becomes.