I dunno Chris. It seems to me if pressure is holding at the gun then volume is there. If pressure drops volume is not there. As I said if he is choking his gun then his volume requirement is decreased below the Iwata spec. That is the only logical explanation I can think of. The gun valve is after the gun regulator….Even if it builds pressure it doesn't have enough volume. Volume is more important than pressure with an HVLP.
It seems this topic is similar to the “compressor making water” topic. A lot of opinions and theories that folks are adamant about.
This subject is bringing back bad memories of mind boggling nozzle calculations in my college thermodynamics class.