How much difference if the tonearm is mounted 5mm

First of all, Hola', Raul!
Second, Dang, are you saying that after setting P2S at 207mm (which is quite short for even a 9-inch tonearm), your cartridge could be perfectly aligned with each of the two grids on the Feickert protractor, including the front to back alignment of the cartridge body? Your tonearm is totally unfamiliar to me; is it "vintage" or a brand new product?  If vintage, the tonearm may have been designed for Stevenson alignment, especially if it was made in Japan.  The Feickert is designed for accurate alignment to the Baerwald standard, which is very different from Stevenson.  (Which by the way also means that you should not use the Feickert if you want to try Stevenson alignment.)  I cannot recall whether the Stevenson is "shorter" in pivot to stylus tip distance than Baerwald or Lofgren, or whether it's the other way around, but possibly this is why your alignment appears to work, but you would have had to twist the cartridge body with respect to the headshell to make it work, i.e., to achieve the proper offset angle so the cartridge body aligns with the grids on the Feickert.  Is that the case?  If so, maybe another mystery is solved.

Third, DSGriffith, I don't really follow your argument, but I have to agree with Raul, who after all is agreeing with me.  On the other hand, I take your point that aftermarket headshells or swapping OEM headshells between two different tonearms may complicate the alignment problem. For a given geometry (Baerwald, Lofgren, or Stevenson) with a given tonearm, theory predicts there one and only one "most" accurate alignment (defined as that which gives minimal tracking angle error on average across the surface of an LP).  (I'm aware that Baerwald is identical to one of the two Lofgren methods, A or B.  Can't remember which.)  I am not one who believes you need to be within a micron of "accurate", but 5mm seems a huge error.  There are cases about which I have read where persons in the field have come to disagree with the manufacturer of this or that tonearm on what is really the best P2S distance, etc, for a given tonearm.  This is true for the FR64; FR says 230mm, gurus say 231.5mm.

Hi Lewm

My main point is not to dispute overhang dimensions but to dispute the assumption that because a templet says a arm is a certain length then the arm that you are mounting "IS" that length. Measure it and then determine what the overhang is suppose to be for the arm that you are mounting.  Not some  factory manufactured arm  that has been made from tooling that has +/- tolerances built into the assembly tools and possibly put together by some guy on Monday morning with a hangover!
BTW: I also agree with what Raul and you have stated.  But text book definitions are not what the question here was.  I think the arm in question does not measure in length for what the overhang dimension given is suppose to measure.  This particular arm just might sound better positioned at a location other than what is printed on a templet.
Regards,

Dear Dang: So, you are saying that PTS distance is 207. Nothing wrong with that if the offset angle and overhang belongs to that PTS distance. You can see it here:

http://www.vinylengine.com/tonearm_alignment_calculator_pro.php?arm1=Arm+1&l1=ps&a1lv=207&am...

as you can read on that chart the arm1 almost follow the Löfgren alignment so it's right, no problem at all. Now, looks like the cartridge overhang is correct because even your protractor points and only you have to be sure that the cartridge offset angle has the same value in that calculator chart to have the levels of traking error/distortions for that geometry alignment. 

The distortion levels beteween a tonearm mounted at 207 or 212 mm from the pivot are almost negligible if in both cases the overhang and offset angle are in the right position. 

Don't worry what the tonearm manufacturer put on his tonearm specs because we can change the effective lenght of that tonearm if and only if we are sure thet the overhang and offset angle is right on for that geometry alignment choosed.

Now, if you are sure of all those critical parameters then your " terrifc " sound posted is just true musical information with distortions at minimum for that geometry alignment.

Regards and enjoy the music,
R.

Dear Griffit: "  I listen to records and know what I 'hear'! ", yes but what you don't know is the distortion levels generated for your choosed alignment till you use " white papers "/calculator of those white papers equations. 
Tonearm/cartridge alignment is just geometry not rocket science but even that you need to work with " numbers " where " subjectivity " is not enough.

Of course that if you don't care  about distortions levels then you can do whatever you want.

Regards and enjoy the music,
R.

Raul, read the opening post.  A tone arm was bought.  Should he drill the mounting hole at the given dimensions per the manual?  You say yes.   Why?  Because the manual says so?  Sorry but mistakes often get made on drawings.  I'm a Aerospace engineer and I have correct hundreds.  Who said that the arm in question actually measured what the manual says they all are expected to measure?  To drill a hole in your arm board because some stranger says that is where most of the arms he has manufactured should be located is just plain wrong!  That arm should be measured. S2P determined.  Then drilled.  It is not rocket science. It is just plain common sense.  We are not talking text book geometry here.  We are talking about one particular tone arm. 
Regards,