Fransisco, Yip does not take a "typical value for this purpose". For SME arms with non slotted headshells, Yip requests that the user supply the cartridge mounting hole to stylus distance in mm. He adds this to the pivot to mounting hole distance of the arm, taking into account the offset angle of the headshell to calculate the actual effective length. This is then used to draw the arc on the protractor. That is why with SME arms, MINT protractors are specific to the arm and cartridge. I have ordered two MINT protractors for SME arms from Yip. They are incredibly accurate.
Good enough: it all depends on what you think is "good enough". I used the SME supplied protractor and it was fine. The challenge is standing over it precisely to align the arm with the outline. How does one know that his line of sight is square? It is an approximation at best, but it works just fine. Then I witnessed a friend use the MINT protractor. I ordered one for my SME V. The first thing I did was check to see how accurate my existing alignment was that was based on the SME protractor. Well, it was off by about 1mm at the outside of the MINT arc and 0.5mm at the inside. The sound was fine, but after I reset overhang with the MINT, it sounded slightly better. Yes "slightly better" is a subjective and relative term, but I preferred the sound with the more accurate protractor. The best thing about the MINT, which is completely absent from the SME, is zenith alignment at the null points. This is another parameter that matters with certain stylus shapes. Without being able to visually check how square the cantilever is at the null points, how does one know if zenith is correct? Of course it matters if the stylus is mounted squarely in the cantilever tip, but the SME protractor does not help here either. I am not aware of any protractor that can confirm with accuracy the mounting of the stylus. Simply aligning the edge of the headshell with the edge of the cartridge may be "good enough", but aligning the actual cantilever with tiny lines at the null points with a 10X loupe is more accurate.
None of this matters if the end user does not hear the difference or does not care about precision. Good enough is always good enough, until it is no longer.
Nice to know you get one MINT protractor for each cartridge. However your comparison just shows that SME and MINT use different alignments, not that one of them is better or more accurate than the other - as you know each alignment has its fans and detractors.
It is only my opinion but I always found these old alignment battles a waste of time. Do you experience changes is sound quality as your LP is being played and tracking error increases or decreases in most of the inner zone of the LP? In fact alignments mostly reflect sound quality at the zones outer and inner than the null points, and are simply compromises between what people weight more - average distortion or maximum distortion.
So in this case, what you call "good enough" is IMHO just another view of excellence.
IMHO much more important than zenith - that in my own current cartridges is negligible, although some well used old cartridges that I have owned have developed this problem - is the zenith of the angle of insertion of the stylus in the cantilever in most stylus shapes. Do you know of anyone checking for it?
Again IMHO the critical tool for cartridge alignment is the accuracy of our sight. And I feel it is possible to do a much more accurate work when the headshell or tonearm are reverse turned in my hands far from the turntable than fiddling in uncomfortable positions. As always YMMV.