KMRUNOUT, I believe that (roughly) half of the cueball's speed is developed during decompression of the various parts of the stick. Otherwise you would have a very inelastic collision and the CB would come away with, well, about half the speed that it actually acquires. (The reason for saying this is a bit technical.) The ball-stick collision isn't as elastic as a ball-ball collision, but it ain't too bad either.
When hitting off-center, during impact the region near the tip bends away from the cueball as the CB develops spin. It doesn't "unbend" while in contact, but continues moving sideways until the cueball is gone. The 'potential energy' stored by the internal bending strains is therefore, in the main, not returned to the CB.
Jim
