Thanks for this interesting discussion but something seems to have been left out. On my 24V the screw on top of the diaphragm doesn't sit in the middle. Hence it can't push directly against the "axe de reglage" (as per Shayne's drawing) or boost compensator pin. I think the screw is attached to a cam that rotates around and by the screw in the cover. Hence turning this screw one turn in will put the cam back into the original position resulting in no change. Rotating it half a turn clock wise would put it in the same position as rotating is half a turn counter clock wise. The rotation in the direction that pushes the pin down will be more difficult than in the other direction. As Shayne points out, trial and error needed here, only in much smaller steps then with a center located screw.