And i'll be impressed if you can do it with a regulator. I tried that with mine and even with 2000psi working regulated pressure i couldnt get 40fpe. There wasn't enough regulated air per shot in the plenum between the regulator and/in the valve.
I'm pretty sure its possible of you increase the plenum size and open up the transfer ports but I came to the conclusion there wasn't enough shots in the Mrod to be worth the trouble at 40fpe.
All that said, I'd love to hear of your success if you pursue it.
"It doesn't get done til someone does it"