Bing 64 needle 912 UL

Changing the position of the needle requires removal of the retaining screw, but if one wanted to do a quick spot check to determine which groove is being used, you could measure the length of the needle from the tip to the base of the piston (assuming the o-ring is in good condtions)

Would anyone have the length (dimension 'A' on the cross section in the attached image) for groove positions 1,2,3 and 4?