Spindle-To-Pivot Distance

Clearthinker, I did not say that the 10mm error in P2S contemplated by the OP would not be audible. At best, I said that if he fiddled with his head shell offset and the slots on the mounting surface, so as to move the cartridge forward, he might at least partially correct for the error. After that, I have no idea how it would sound, any more than you do. So sorry if that bothers you. Not.

@lewm , think about it. He is mounting a tonearm that requires a 250 mm spindle to pivot distance at 240 mm increasing overhang by 10 mm. In order to get the right geometry you will have to push the cartridge back in the head shell, back towards the pivot not forwards. Then you would have to twist the cartridge clockwise to get the right offset angle. Moving the cartridge forwards will increase overhang eventually with the results I mention above.

@rauliruegas , That is the most eloquent post I have ever seen you do and you are absolutely right. Anyone who thinks they can hear even 5 degrees of tracking error need to run some blinded tests on their own to learn a little more about their hearing capability. People need to run these experiments to learn what they can and can not hear along with the degree to which your brain can play around with you. 

You have run into the problem that I mention in regards to linear trackers.
The vertical effective mass is too low for most modern cartridges and the bass gets screwed up. This is the reason Clearaudio made the Goldfinger so darn heavy. It makes their arm sound better. Terrible arm IMHO. Just watch one tracking and you will see the cantilever lead the arm and wiggle back and forth. Air bearing arms do the same thing perhaps not quite as bad.
Have you had a chance to hear a Schroder LT yet? I love that design.

Mijostyn, good point but it seems to me we’re both right. Moving backward would preserve overhang at the expense of reducing effective length. Moving forward in the headshell would preserve effective length but increase overhang. Both work if you can also twist the cartridge. Neither solution is orthodox.

@lewm, I think my point is that you can not conserve the effective length of the are because as you increase overhang you shift the force vector clockwise to the point that the stylus can no longer maintain contact with the groove. Buy moving the cartridge back and twisting it clockwise you are turning the arm into an appropriate shorter arm which works at a SPD of 240 mm. I believe it is the only correct approach other than getting an arm that is the right length for the turntable. 
@rauliruegas , what is your opinion on this?

"You believe", is fine.  There really is no "correct" approach, since to begin with there is a built in error that will affect any solution.  Can you further explain what you have in mind as regards the effect of increasing overhang, to shift the "force vectors"?  Are you thinking of the skating force, or what? Of course, you would have to change the headshell offset angle, or twist the cartridge in the headshell, in my "solution", just as for your solution.