Drop gage connection to stand

Having issues with Drop gage on a granite stand I've set up. Cannot get to stablize correctly. Arm that attaches to back of gage has a vertical pin and spindle and there are two sets of clamps holding on to bar with tightening nuts. found by moving one or both the clamps produces different readings. Had gage extended to full range but was getting better results at about half. Any documentation or information on correct set up for drop mics?