[Zippiot]

its actually quite simple to make a pneumatic cylinder that can stop at any point. all you need to do is attach another solenoid to the exhaust of the cylinder's solenoid. it's very hard to describe, and i may draw up a pic in the next few days, but essentially u make it so that at any point in time you can cut off the exhaust of the cylinder, so both sides will fill with air, effectively stopping the piston in its place (or very close to it). but the purge can be very violent, otherwise all you need is enough buttons to manage it. if this was too complicated i can try to make it more clear just ask.