The range ability of all the parts of the system does gives the useable range of the system. (Your throttle range?)
The term is rangability. That is a ratio of maximum controlled flow over the minimum. It can be use to compute throttling range. Throttling range is the difference of the control point at wide open to closed valve. In this case the control point is a pressure and if the setpoint is .25 PSI and the regulator valve is wide open at .3 PSI and closed (or at its minimum) at .2 PSI then the throttling range is .1 PSI . Both are unknown. But I believe that both the rangablilty and throttling range of a Cline or Iron Bay is smaller than a Perry Pump and of course at a lower pressure.
Also not after 2 minutes idle as you write in post 30, that’s a bad (de)sign for an engineer, so back to the drawing board when there isn’t a fault in the system.
That is what happens when someone puts a check valve in the muffler pressure line to the tank. The tank keeps its pressure up till the engine uses some fuel. It may take longer than two minutes. Those who swear by this probably never left the engine running at idle long enough to find out, so it may work well for them. If it takes ten minutes then it would be long enough for almost everybody and may be a good system for many.