Pneumatics Rookie Problem

[Squishylizard]

Okay, I've searched on the forums for the answer to my question but either it's not there or I'm using the wrong search terms.

Regardless, what I need to know is how to get this setup to work if possible:

4 accumulators at 120 PSI
4 2" Bore 12" Stroke cylinders at 60 PSI
Compressor (maybe)

How do I hook up the solenoids so that the cylinders are not pressurized until I want them to extend? ie, there should be roughly the same amount of air in the tanks as is needed to fill the cylinders (2" x 6" at 120 PSI vs 2" x 12" at 60 PSI), so what kind of solenoids and linkups would I need to transfer the air? The cylinders only need to be extended once but then they need to stay there at the end of the match.

Thanks muchly for any assistance

EDIT: I just realized, that with the fact that air wants to equalize pressure, that opening up the accumulators to the cylinders will only result in them being pressurized to 30 PSI. What I need to know now then is how much force the cylinders put out at half pressure, and how fast the compressor could put in enough air to bring the cylinders to 60 PSI.