The Scout Walker who takes the dominate position in "the piston" needs to be chock-full of energy, as they're going to battering their partner with fast'n'furious motion, almost bouncing them between your base and your feet. You don't need to be quite that vigorous and can actually get quite a nice slow motion going, but its bound to happen near the end when you're both really going for it and screaming "faster faster, harder harder" if you get what I mean. Until then take it easy and have a good turret-twisting snog while you're at it.