How much difference if the tonearm is mounted 5mm

Let me make it clear. When i mounted the arm as the manufacture suggested, 212mm STP, the cartridge could not reach the cross point on my Dr. Feickert NG Protractor (I extended the cartridge all the way out from the Pivot) it was 4mm short. Unless i have a longer head shell or i will have to mount the arm 4mm closer than spec. (5mm to be sure).
If I mount it closer, and use the Protractor to align the cartridge, will the arm be performed as normal?
Thanks to all who have responsed so far.
Calvin

If you mount the arm the 4mm closer I would suppose that it would be fine...(Harry said he or anyone else can not detect a bit off)...however, as for ME....I would want it absolutely correct. ....just a question....why would you want to exchange arms...VPI makes a very good arm...the 3D is wonderful.

Hi Stringreen,
I am adding a second arm on my turntable. My turntable came with the JMW 10, so the armbase does not accomodate with the new arm wand. I have to change the whole set to the 3D, a bit expensive right now.
As fir the new arm, it is shorter than spec. Hence the question.
Thanks,
Calvin

Calvin ... did you try a Baerwald (sp) protractor? Just curious if you still come up short.

Hi Bifwynne,
Yes, that was the one I use to set up the cartridge at first. I also checked the leveling of my table and armboard. As of right now, i beleive that the arm is deffected. It was made shorter than the specs by mistake.
Thanks,
Calvin