I would send back the adjustable regulator, I have never had good luck with them. It is easy to shim or cut coils to increase or reduce pressure. As you found out the only difference between the hi pressure and std pumps is the spring. If you want lower pressure the logical thing to do is get a spring from a std pressure pump. If you can't find one or don't want to cut yours, PM me I should have one here somewhere.

I just changed from Brad Penn 10-40 to 5-30 synthetic in my hemi with a high volume melling pump and the cold pressure dropped from 100 to 75 and hot at idle went from 65 to 37. Go's up to 50 by 2,000 60 by 3,000 and maxes out a little over 75. It's nice to see the pressure changing instead of being maxed out all the time.