The vertical slime block/piston launchers unfortunately injured my horses on trial runs even when they landed fully on a large pad of slime blocks...a cool idea good for players but not for animals so I removed them - but check out the horizontal version using ICE BLOCKS! It works exactly like you think it would, giving the player a quick push and sending them about seven ice blocks or so. I'm surprised I haven't seen YouTube videos of human pinball machine mods yet. Stuff to play with....