Or buy an adjustable pressure regulator with a low pressure range. Its all you are building anyways.

In fact I am selling the adjustable MBC out of my porsche since I am replacing it with an EBC. Its a locking type so you don't have to worry about it accidentally turning and going out of adjustment.

If you run some pressure hose through the fire wall you can even set up cockpit adjustability with this one.

$50 OBO. PM me if you are interested.

You can see how its mounted in my car just to the left of my clutch pedal.