How much difference if the tonearm is mounted 5mm

To ME....a little off means the cartridge goes back to the manufacturer.  I can not condone the lightening of the wallet to the tune of thousands (or even hundreds) of dollars.  I can not accept sloppy manufacturing.  A little off means I cannot trust that cartridge to be what I purchased.

5MM no problem if you like crappy sound.

ebm,

You are correct if that is what the final setup actually measures. That the position of his actual arm is 5mm out of the correct spindel to pivot dimensions for the length of his actual arm. 
5mm off is 5mm off!  But what is implied from the beginning of this thread is that there is 5mm difference between the the information given to make this setup and what the actually set became!  One of the two options is right and the other was wrong.  Is it the final position of the arm that is wrong?  The owner of the arm says it sound terrific in its current location.  This location is 5mm off from what was stated for it to be positioned.  Because 'crappy sound'  has not become the outcome of him moving the mounting hole over by this 5mm, then I would say that the spindle to pivot distance number he has been given was incorrect. His is not incorrect to have set up his arm correctly, only incorrect for not using the numbers supplied.  If 'not crappy sound' is what his goal was, then what he did was correct.  If following supplied dimensions  was his goal, the he was wrong.  I would prefer the 'not crappy sound' outcome over the following of supplied dimensions!
regards,

Dear EBM: You can read some information of what I posted.

Now, if in that tonearm set up: overhang, offset angle and pivot to TT center spindle distance belongs exactly to a determinated geometry alignment like Löfgren, Baerwald or whatever then that " crappy " sound will not appears.

In one of my links ( VE calculator. ) I made a comparison between different PTS distance in specific for those 5 mm. The calculator gave us the values for those 3 parameters I name it  ( in both cases. ) and gave us the diagram where we can see the differences in distortion levels and if I remember when all those 3 mparameters are right the distoriton levels are almost the same. So, IMHO no crappy sound.

Regards and enjoy the music,
R.