FX regulator adjustment

Ok, I have been shooting my .25 Impact for about a month now. I want to start tinkering with the settings. The regulator gauge is pretty coarse. I purchased a couple of Huma gauges and replaced the fill gauge, but the rear regulator gauge will not fit. Is there a gauge that has a finer marking that will fit in the recessed or maybe a pressure instrument you connect to set the regulator pressure?
 
Hi,
I got he Huma gauges for my Impact .25 and yes the regulator gauge doesn't seal properly owing to the fact that it hits the bottom of the gun before it bottoms out in the "well"
I contacted FX USA and got the plastic washer for the threaded well. It still didn't seal right so I dug around and found an 0-ring that fits the diameter of the reg gauge threaded shaft and now I'm good to go. The pressure there is only 120 bar or 1740 psi so you don't need a real hard o-ring. Hope that helps.