Feickert Protractor - anyone use one?

I guess I did not make my point very well, but for me the beauty of the Feickert is the cross arm that is graduated in mm, with a vertical spike at the far end that can be set down on the pivot point exactly.  If you measure P2S with a conventional ruler of any kind, there is that awkward requirement to estimate that you are "over" the desired location of the pivot; if the ruler does not lie in a horizontal plane parallel to the pivot point on the tonearm or the blank tonearm mount, there will of course be an inaccuracy due to parallax.  The Dennesen and even the original version of the UNItractor, incorporate cross arms that are not marked in units of distance.  (I am guessing that this fault has been remedied in newer versions of the UNItractor, because I think I see in photos that the SMARTractor includes a crossarm marked for distance in mm; the SMARTractor is less expensive than the UNI.)

Amen to that lewm !
There are a FEW TT's with something sticking up from the pivot you can sight on with a 50 buck Geo-Disc and get 'er done but not many .

Lew, another method which I've done over the years is to create a template out of sturdy stock such as a file folder.  I have basic drafting skills so can lay out a line with the exact center hole for the spindle, the P2S distance from that to arm pivot point, and then mark that with a vertical needle.  Rather than attempt to cut out a circle for the spindle I found a simple X cut with an X-acto allows the template to be fitted over the spindle.  Anyway, it worked for me.

My above post assumes the arm does not have a factory mounting template.  Buying used arms typically eliminates that convenience.

I use AccuTrak arc protractors for my arms.  I have a TT where I can adjust P2S distance easily.  I think this point was made earlier, with Arc protractors you don't need highly accurate P2S measurement, just need accurate enough to get within the overhang adjustment range of the headshell. When you are on the arc you have the overhang correct.
For most cartridges where the cantilever is visible, the AccuTrak allows for very precise adjustment of zenith. Especially with a magnifying glass.  For some cartridges, a mirror would be helpful.  All this being said, if money grew on trees, I would enjoy using the SMARTractor which seems to offer all these features.