Re: Two regulators for one piston
 

Our team was looking at a similar question a few days ago. Originally I was going to go the route of 1 valve on each side of the actuator, one at 60psi and one at 10psi. We found that as other have suggested that the http://www.andymark.com/product-p/am-2032.htm would be an easier way of doing things with the same goal achieved. I think either would work fine, but you would need to follow the rules about multiple regulators, I believe that there are some additional restrictions, such as having another gauge.

Re: Two regulators for one piston
 

Please try the experiment. What you will find is that the pressure is identical on both sides of the needle valve. These devices restrict the movement of air by making the orifice smaller. They limit the maximum kinetic energy (flow) without changing the final potential energy (pressure).

A flow restriction could be what you want if you are happy with the maximum shooter distance and what you are trying to do is create a slow piston velocity for a shorter shot (soft pass).

It will not work for the original question where they were trying increase the maximum velocity by presenting different pressures to either side of the piston. Asymmetric pressure is valid if you require less force to reset the shooter than to make the shot. Less pressure on the exhaust side will limit the required exhaust flow (less air to move) and increase the velocity of the piston. To change the pressure, you need a pressure regulator.

Re: Two regulators for one piston
 

I know what the OP wanted. I was merely expanding on Matt's post about the flow control valves. Thanks for the explanation.