Agree 100% with you on the distortion which is why i tried to make a parallel with TAE. I find it highly unlikely that every tonearm cartridge combo will respond to TAE in the same manner and there is more to it than simply slapping a number on it and calling it equal. I think we can all agree that the lower the TAE the better but If we accept the belief that the lowest TAE is best then a 12" arm must better a 9" arm which is a statement that will draw lots of ire here. Going further a linear tracker would be better yet. With the new 9" sapphire arm, Kuzma counters this by saying arm rigidity is more important than TAE much in the way Viv labs asserts Skating forces dominate the situation. I see nothing technically inconsistent in any of the Viv labs assertions to merit calling them "stories" or deceptive in any way but it seems some here feel differently.
WRT cutting level and mistracking, it seems there is not a good definition of what mistracking actually is. My take is any movement in a direction not cut on the record is mistracking which means it is constant occurrence from numerous causes. I think the concept of "If it makes it across track 4 on record X it is a great tracker" is a far to simplistic all or nothing approach. The devil is in the details and lots of things come into play here and exploring the details is the best we can do.
If the coupling isn’t there as I have talked about, one of the results is more mistracking. IOW it works opposite of what you propose. This is simply because the arm is putting more energy into the cantilever.
Like distortion and TAE, mistracking cannot be a one size fits all proposition and making it thus is going in the wrong direction. What if it is the type of mistracking is what matters? I have found that comparing a conical to an advanced profile for a given angular error nets interesting results. For angles in the ±1° range the advanced profile is substantially better but once outside that range the conical becomes the preferred choice. IOW 5°≠5°
Regarding your last question, how do you know that underhung arms are actually preferred? Do you know of a poll regarding such??
Didn't mean to suggest that. I simply noted that amongst the specific subset of Viv Labs arms, the 9" arm seems preferred to the longer versions which is odd if TAE is the true metric of quality some make it. I do want to be clear that with my current setup (traditional offset overhung rigid bearing arm + advanced profile stylus), I find more than 1° TAE problematic but by comparison the same profile (microrisdge) on the underhung Schröder reference reminds me nothing of what I would expect hear from a similar error on a traditional arm. This simply tells me that there must be more to this than simply looking at the TAE as a single factor and explains my interest in this thread. Do I ultimately expect to become an underhung fanboy??? No... but that doesn't mean there isn't something to be learned from those who like it ~17mm short :-)
dave