I was recently interested in this subject. I was paying more attention to the accuracy of the tonearm geometry of my VPI Classic 3 Sig SE and the Feichert universal protractor. Upon using the Feichert, I'm measuring 260mm STP. After going to the VPI site, the best info from HW was 258mm. So, I asked THE question. I was told by the administrator, brf, to loosen either or both the armboard platform screws or the arm mounting board screws and use any slack, to compensate for any difference. Neither worked. So, I just paid around 5k for a tt that hasn't even been machined correctly to conform to industry standards. I also asked if Harry's supplied gauge is based upon any of the (3) standard geometries. I have yet to receive ONE answer. WOW!