I'm using the Hoke 1300
Really? I don't have any problem fine tuning with it. I only keep my regulator around 20 psi though. Perhaps you have it opened too far?
It's Oxweld brand any good? Lots of these on eBay.
Wow! that is a steal! I paid $100 for mine and it's not SS.
The Dennerle is a dandy of a check valve. I doubt that would be the problem. Are you getting a consistent pressure reading on your lower gauge? Perhaps you have an internal leak as Alan suggested? Did you run the test he posted? Hopefully he'll chime in.