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?

I know I’ll get hate mail, figuratively, but anal attention to alignment is overrated in my opinion, as regards the effect of slight misalignment on audible distortion.

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

So if you go by there methods you have 2 null point with everything is supposedly perfect and the rest goes into various degrees of distortion. Love to meet the guy ,without seeing the record, who could pin point the null points with his ears

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Good answer.
https://youtu.be/k9DO26O6dIg?t=135

What will happen, if you use a 240mm P2S distance where 250mm is recommended, if you do nothing to compensate for that error, is the null points will move farther apart from each other.  If the tonearm is designed for an algorithm like Stevenson, where the inner null point is already close to the run-out grooves, then there is a danger that the inner null point will now lie IN the run-out grooves or even on the label itself, where of course there is no use for it.  But if the tonearm was designed for one of the other two popular algorithms, the inner null point might still be useful on the playing surface.  That might be no big deal at all, depending upon the LP. But of course also the tracking angle errors before, between, and after the null points are traversed will be altered, probably increased in magnitude. (I haven't done any math on that.)