I had trouble getting below 5# on a recirculation style plumbing thru the carbs. With a dead head regulator at the loop end, before return, the psi was 6-7#. When I removed the regulator restriction I only got down to 5-6#. I tested a few ga just in case.
My latest bright idea is to T a dead head reg to carbs off a intake-return loop dialed in to 10# with a BP/blow-off style reg.
Below is a pic of bright idea #1 with the loop thru the carbs ending in a dead head reg to return.
