I've taken some of my Ninja-style regulators apart and added shims to the internal spring stack to increase pressure. More shims increase the spring preload, requiring a higher pressure on the low pressure side of the regulator to stop flow.
I've also added shims to the face of the valve (around the pin valve) to get the orientation of the reg/gauge where I wanted it. Those shims are much larger diameter (20mm?) than the internal shims used to adjust pressure (9-10mm?).
I agree with Walter that the pin valve is either closed or open, either allowing air to pass or not. Even it if's just barely open, it's still open, allowing air to pass, just more slowly=less flow as previously stated. Add too many orientation shims (a bunch) and the bottle won't thread in far enough to the female fitting to depress the pin and there will be no flow.