Controlling the gravity drives is quite simple really - you see Cap'n, you can imagine the g-field as a spring tethered to a particular point in space, dragging you toward it, and you just need to tell the drive where to put that tether! Well, we have a computer tell the drive anyways, hooked up to the movement of the wearer's legs to make it easy for the Hands to get used to it. Just be careful: anti-gravitic circuitry reacts violently when exposed to Chem.