it wont prevent you over locking the rear, it just makes your cylinder stroke shorter, the pressure produced by the pump is not affected by a chain on the axle LOL
It will however prevent you 'over extending' your cylinders causing them to stick, but thats not quite the same as 'overlocking' due to pressure
chains do 2 things. use them as a power teeter toter to pull one front wheel up (standing 3 wheel) as the cylinder pushes the frame up, the chain behind it pulls the rear of the car down,forcing the front up. or some cars with alot of lift have axle/driveshaft problems and need to be limited in certain motions. I've actually seen some fwd cars that had to have chains or the rear would fall out.