[Enigma's puzzle]

If you need to increase the force coming from your piston, and/or speed it up you could always consider adding a spring or tying some surgical tubing in a way that it will assist the firing mechanism(up to doubling the power of a single piston stroke), however if you lose too much pressure, you may not be able to retract the pneumatics quick enough to abide by the rules.

I though id throw this power and thought generating idea out for you to kick around.