Above photo: A Clearaudio alignment protractor is used to set overhang and offset angle of a Thorens TP16 MKI tonearm with Shure V15VxMR cartridge. This protractor uses the pivot to spindle distance as an integral feature of it's process and relies on a single null point.
The protractor above may not be practical for many as it costs $150 US at the time of this writing.