LP tank regs don't increase efficiency. Ninja themselves admitted that in a thread on pbnation. Running too low of pressure can also starve a marker if you don't have enough pressure gradient.
My experience which may be worth jack is that people had markers with crappy secondary regs, they went from a HP to a LP tank and the secondary reg output dropped which lowered their chrono. They feel like they get more shots but its because they are shooting 10fps slower on the LP tank.
I tested an angel mini reg once (garbage, I hate them with a passion) and going from a 450 to 850psi tank raised the output pressure by 50psi. I tried the same thing on a sidewinder and it made basically no difference, because AKA is baller.