Spindle-To-Pivot Distance

10mm error in PS distance is too much! 

But theoretically if you have detachable headshell with long slots for the mounting screws you can compensate 10mm. In the end it will be ugly as hell. Your cartridge will be moved way too forward in the shell (10mm more) and twisted a bit. 

I would’t do that, you’d better change the armboard with correct mounting hole for your tonearm and given PS distance (using original template). 

What’s your tonearm?

Why would moving the cartridge forward in a headshell with elongated slots “look ugly”, and who cares?

Do you know what is 10mm ? Try to move a cartridge 10mm forward than usual, it most cases it’s impossible to move that much. The difference between alignment methods is within 2-5mm max, no one have to move a cart 10mm forward in normal situation. And we are talking about different detachable headshells. On a tonearm with fixes shell the slots are much shorter.

I have over 30 different headshells and very few of them (with overhand adjustment like AT Technihard) will allow me to move a cartridge 10 mm forward than normal position which is usually in the middle if the slots. 5 mm is ok, 10 mm forward is too much and in this position headshell is behind the 1/3 of a cartridge body - this is ugly. Normally a cartridge body is under headshell.

Most of the audiophile are excited about ugly things, but in my opinion OP can change the armboard instead and everything will be perfect if he could.