I'm not an expert on pump physics, or interpreting specs, but I'm with him
Use a mechanical regulator to control pressure, one that spills excess
fluid volume back into the reservoir through what's usually called a bypass
valve. Then control flow volume with the speed of the pump's rotor.
You could still experience problems at extreme combinations of low
pressure/high volume or high pressure/low volumes. Impeller pumps rely on
centrifugal forces, and can stall out at low speeds. A vane pump is good at
maintaining pressure at low speeds, but the vane's edges are a wear risk at
A link to a good tutorial on pump design would be a handy thing to have
right now. The relative size of the nozzle's opening to the desired rate of
flow matters, too.