I have been using a Mint protractor with my VPI Classic for around 6 years. I've mounted 5 different MC carts with it. If it's printed on the mirror, then I use it. So I put the stylus outside of where the record starts (near the protractor's printed arc starting point), check alignment to the arc and then move it near the spindle (far inside of any run out groove). I always figured if it follows that line all the way through, then that's as accurate an overhang as you can possibly measure for.