First and foremost, every time I see Phoenixengineering participate on this Board I smile. He is a great all-around guy and has a wealth of useful knowledge.
Now that aside, as someone who gave up on VPI decks (three of them) and went to vintage decks on custom plinths and Reed 3P arms, I have learned from personal experience that P-S is not a demanding spec if you have a typical headshell that allows the cartridge to slide back and forth. I have learned from mounting my own arms that a tonearm's manufacturer's specified P-S may not allow for all modern cartridges to come into optimum alignment. You may argue that this is the fault of the tonearm manufacturer but such is not necessarily the case-often it is due to the cartridge manufacturer having an unusual stylus to cartridge body mount configuration.
Case in point would be my current VdH Crimson Strad. When I mounted my 10.5 Reed 3P to the spec'd P-S, I could not move the cartridge far enough forward to get to the Lof B on my Feickert alignment grid. Remounting the arm a few mm's further away from the spec'd P-S allowed me to the to that point.
Brian Walsh of ttsetup.com confirmed that what I had done is the only approach and that it does not, in any way, compromise performance-he was able to accomplish optimum alignment with his very sophisticated software based tools.
So imho HW is correct that being a mm or two or even three is not a problem if the stylus can get to the desired point given your alignment type/choice. To put it slightly differently, the stylus does not know or care about the P-S distance. P-S serves as a range within which most cartridges can be optimally aligned within the slots. I have said this before and will say it again-the SME approach to P-S proves my point: no slots and instead the P-S is changed for each cartridge using their ingenious pivot point sled.
