Getting back to the original post. I just don't see how adjusting the HS could have no effect whatsoever unless the tool you are sticking through that hole is not actually engaging the hammer. Can you turn it until it makes a full stop in either direction? That hole in the hammer is not likely to be directly beneath the hole in your stock. You may have to rotate the whole thing till it lines up. I can't help thinking it's that simple and we're just over thinking it.
If the gun is shooting on the "plateau" with the minimum HS preload at the regulated pressure, then increasing the preload will only give more dwell, and use more air (and make more noise).... If the valve is open until the pellet leaves the muzzle, no amount of extra HS will increase the velocity further.... The HS on a Hatsan is designed to create a bell-curve starting at 200 bar, peaking at maybe 140-150 bar, and then after that the velocity will drop as the pressure drops.... By definition, if your regulator setpoint is toward what is the lower end of the bell-curve pressure, you are operating on the "plateau" at that pressure, and would expect that increasing the HS preload would not add any velocity....Bob