rebound affects the "pack" in the shock under compression. there are a few theories about that . since the dawn of bladder shocks has removed the air bubble fron inside the shock body itself, the piston pushes up on the fluid over the piston and compresses the bladder in the shock cap. personally i perfer less rebound as I perfer the spring to return the piston to the static position. Truth is, it is very rare that your shock bottoms out , unless you hit something. Concider pack or rebound like the valving in an automotive strut. basically no rebound means the shock will have damping on the return stroke. 50% return is like having a 75/25 stroke and return. I use much less than that , more like 25% rebound. just a preference i guess. for that matter too much rebound is a recipie for leaky shocks and blown out o-rings .. just try to make them equal.
