If you're concerned about your headshell slots having enough 'play' to allow you to mount a specific cartridge, I'd suggest you first print out an arc protractor on conrad hoffman's site http://www.conradhoffman.com/chsw.htm, using your measured Spindle to Pivot, as a test before you order Mint's device. Also, maybe doing that will help convince Mint that the StP that you've given him will actually work.
MintLP arc protractor
I'm talking to Yip about a protractor for a Rega RB-300 mounted on a VPI HW-19 Mark III. To verify the desired 222mm spindle to pivot distance I cut a piece of cardboard 222mm in length. I measured from the spindle to the center of the armboard mounting hole. It looks to be spot on at 222mm. Is there a more accurate way to measure so that I can confirm my initial findings?
Wendell
Wendell