Spindle-To-Pivot Distance

Guys, forget the null point issue. It is not the problem. Overhang is the problem. Getting the right overhang would require sliding the cartridge back in the head shell towards the bearing. There is no arm I know of that is that adjustable given the limits set by the turntable. Running a tonearm with an overhang 0.5 cm over spec increases the skating force. The force vector will shift clockwise as the tonearm travels towards the spindle and eventually the stylus will pop right out of the groove and arm will zing right across the record with obvious results. 

You will either have to manufacture a special tonearm board as jasonbourne52 recommends or get a 9 inch arm that will fit. Long arms are not a panacea. They do lower tracking error but at  significant expense. Many of us, myself included think it is a raw deal. 

@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.

@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?