Mint LP Best Tractor---HELP

Correct me if I'm wrong, but my understanding is that the creation of this arc style protractor for a particular turntable/tonearm combination requires the accurate measurement of the distance between the platter spindle and the tonearm pivot. My question is, if this is true, exactly how precise does this measurement have to be?

Recently I ordered one of these, got it, and realigned my Dynavector 17D3, which had previously been aligned with the jig that came with my VPI Classic 1. When I listened after aligning the cartridge with the Mint lp protractor, I didn't like the sound I was getting, it just didn't sound "right", the VPI jig alignment sounded better to my ears. I had a sick feeling the spindle to pivot distance that I gave Yip was wrong, so I remeasured it with a better ruler than the one I had used originally (which, I'm embarrassed to admit, was 2 rulers carefully taped together because I didn't have a long enough one). Sure enough, I had given him a measurement that was 1mm short. Sh****t...

So I emailed Yip and told him the problem, and that I wanted to order a new one based on the correct measurement. To my surprise, his response was: "it may not be unfit. I urge you first to check all parameters before making a move.I would like to find out if the stylus tip falls on each and every point on the effective length curve as printed on the Tractor."

Huh?

I thought the whole point of this very well-loved Mint lp Best tractor was the extreme accuracy with which it aligns cartridges. So why would he tell me this if the measurement I gave him turns out to be 1mm off? Doesn't that specification have to be right on the money? Isn't that why I had to order a custom made one rather than one of the ready-made ones he already has in stock? Yes, when I line everything up correctly the stylus tip follows the curve faithfully, but why would that make everything right, wouldn't it do that wherever the arc was printed on the mirror?

I'm confused guys, please help me out here...