Here's the most important alignment fact I know: with all the protractors it's a best guess as to whether the line to the pivot is on the 2 dimensional point! Q.E.D. - lining up the stylus and cart on the grids is also a best guess so obsessing over millimeters ain't get you better sound. Listening will. Download the Enjoy the Music protractor. It gave me the same results as the mirror one I bought.