Rtollert/All,
This where of course where you sort of leave me in the dust, math is not my forte. I do understand, note, and agree with the fact that many different forces are all taking place simultaneously on the Stylus-Groove Interface, and all do impart thier sonic qualities.
You are no doubt correct that incorrect anti-skate will impart incorrect geometrical alignments of the Cantilever, and in turn skew the Stylus in the Groove Wall, something that is no doubt highly critical, especially with a radical line contact-micro line Stylus.
But isn't this something that should be dealt with, with anti-skate settings, rather than us end users perhaps trying to compensate by intentionally skewing our zenith angle to achieve optimum settings-results?
About the only contributions I can offer and note in my personal experiences, is that this was one important area which I feel the Mintlp Tractor very easily surpassed the abilities of the TB Tractor.
Before I set out to use my newly recieved Mintlp Tractor, I sat down for a number of minutes, Table in front of me, and checked my previous setting with the TB Tractor. All looked well in regards to alighment, both as far as overhang, and zenith angle were concerned. I used the exact same methods of using Yip's lighted magnifier, and his "Lupe" as he calls it. (Loupe)
From what I could determine from the TB Tractor, I had a perfect alignment. The Cantilever (at rest at least) was perfectly aligned, with Stylus precisely touching down within both Null Grid's little reference square.
Then I swapped out, and began with the Mintlp. Firstly, I immediately noted that my Stylus was not properly tracing the Mintlp Arc, being slightly short at arc beginning at edge of platter, and slightly long at inside travel of Arc. I estimate my errors at both ends of the Arc were +-1.5mm to 2mm.
I at first ignored these errors to then go to both Null Grids, and see what degree of errors there were with the Mintlp. The errors were slight, perhaps less than +-1mm, but they were unquestionably there. The Cantilever was as well skewed slightly crooked at Both Null Grid Lines.
The reasons I conclude for these differences, was one, that the resolution detail of the Mintlp being much finer, finally allowed me to correctly see for the first time these not before seen errors, two, the design principals of the sight line LP Tractor is a shortcoming, thus allowing a somewhat vague interpretation of accurately sighting the exact precise center of the Tonearm Pivot, even using Doug Deacon's smart suggestion of enhancing the accuracy of this tractor with a piece of fine thread to aid in pointing the Tractor.
And perhaps lastly, and this is a possibility, and one that entered my mind, how great of a degree is/was the quality control of the TB Tractor, to insure correct, exacting placement of the Sight line, the positioning of the two Null Grids, and last but not least, where the Hole was drilled for the Spindle, as any slight error for the hole placement would completely skew the hoped for accuracy?
Of course, the same concerns would hold true with any similar Protractor, that extreme measures were taken to insure a perfectly accurate geometric tool.
With all that being said, (whew!) Wouldn't then an inaccuracy with achieving both highly accurate Overhang, and Zenith Angle only compound-worsen the errors you previosuly mention? I would assume so.
Mark