Dear Thuchan, dear Downunder, originally I designed the UNI-Protractor as a tonearm alignment instrument. Measuring P2S is a matter of tonearm set-up and should be done prior to any alignment (usually you have to drill a hole in an armboard and so the mounting distance is kind of "pre-determined" before starting any alignment).
That's why P2S-measuring wasn't include din it's design. I now realize, that including the stainless steel metric ruler kind of woke up the wolves....
In any case - I will come up with an add-on to enable precise P2S measurement with the UNI-Protractor soon. This will NOT need any alternation to be done to UNI-Protractor and will come with a precise manual and installation instruction.
It will be a 5-minute plug'n'play device.
However - please accept my initial concept, that in my - sometimes strange and weird - mind, P2S was not an integral feature nor request in an alignment instrument for tonearms.
I still think that P2S is a part of tonearm set-up.
But - I will address it due to "public demand" ...;^) ....
Cheers,
D.