Somthing to note, On my setup, I did not use a schrader valve to fill. I had a quick connect fitting (male) on the end of my gage that I plugged into a standard female quick connect. The only schrader valves in use were the ones on the tires and 1 additional on the manifold FOR THE PURPOSE OF DOUBLECHECKING THE MANIFOLD GUAGE.
Many people (including the local hose suppy shop) doubted this would work..I proved them wrong, it does work (at least for 4 very large tires) and if you doubt it, try i yourself...... you may be suprised.
Good Luck!!!!