Thank you for your posts
I probably caused confusion by calling them cylinders, I am more referring to actuators (rams) than cylinders (fire extinguishers etc.)
I have a feeling the standard 3/8" ports on the off the shelf hydraulic rams are not large enough to allow the flow of a full pressure system. Am I correct?

For our hydraulic set up in Andron4000, we bought an all in one unit from related fluid power. It has a 2 liter tank, 5l/m and runs 24V from a solenoid, so we have a turnigy relay switch to throw it on and off.
The valves are attached to the all in one unit and I think from memory we plan to use another switch to throw them too.

I should probably add that we are yet to get any of this working yet as we are still waiting on our weapon parts to be manufactured!

http://www.relatedfluidpower.com/products/power-units/
https://hobbyking.com/en_us/turnigy-...-switch-1.html

The testing and certification was a concern for us on these, so we went for new, off the shelf parts and read the rules very carefully, and made sure to stay within them ie, no stored pressurisation, invertable, incorporated pressure releif valve, test gauge point