How much difference if the tonearm is mounted 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,

ds, Have you really observed such errors?  I am putting myself in your shoes.  In my thought experiment, I have a new tonearm, and the manual says to mount it so as to achieve a pivot to spindle distance of 215mm (for example).  What measurement would I make of my sample of said tonearm in order to know that following this instruction would be a mistake?  I guess that could be distance from pivot to center of headshell slots, for one example.  But manufacturers don't often even supply that spec.  So how did you know that you had a "bad" sample of any particular tonearm?  I respect that your training and life experience may have equipped you to detect and solve such problems better than I.  In my imagination, badly made samples would be more likely to have out of spec bearing friction, much more likely than to be significantly (could define as +/-0.5mm???) longer or shorter than specification.  As I noted above, there is also the case where thorough analysis of the geometry might lead one to prefer a different P2S for a given tonearm from that which is recommended, but that still assumes all of the samples of that tonearm are alike.