[KenWittlief]

I havent thought this through all the way, or tested anything , so Im reluctant to draw up a schematic. Someone might take it and base their design on it, only to learn much later that it wont work for some reason.

The basis idea I have is this. The pnuematic valves work buy releasing the full pressure in the line (60psi) to one end of the cylinder, and venting the other side open to the room - so its like one end of the cylinder is always disconnected.

The big valve they give us also has fittings for the vent outputs - so you could connect those to another set of valves

that would allow you to control the 'open' end - and instead of releasing all the air, contol how much is released

the second valves would not be connected to the pressureized line at all - they would be vent control valves

so when you pressurize one end of a cylinder, then switch it the other way, the first end will not loose all its air, unless you open the additional vent control valve - and depending on how long you leave it open, the air in that side will be allowed to vent out, a little, a lot, or all of it

and that should control how far the cylinder moves towards the other end, a little, a lot, or all the way.