If you're close you can make up the difference with overhang adjustments most of the time.
Once I installed a RB300 Tonearm on a Linn LP 12. The armboard on the Linn was drilled for a Linn tonearm. (I only did this as a stopgap until my new Linn armboard came that was pre-drilled for the Rega tonearm by the way)
I think the two are different by 7 mm or so and the Linn arm hole is larger.
I moved the Rega tonearm around in the larger Linn armboard hole until I was about 3 to 4 mm off. Then set the overhang so that it hit both marks and to my surprise it played just fine.
No inner groove distortion, no odd sounding bass or high or mids or anything out of the ordinary.
About 2 days later my new armboard arrived and I quickly replaced armboards and set up my table again. I can't say that I heard any difference at all.
Once I installed a RB300 Tonearm on a Linn LP 12. The armboard on the Linn was drilled for a Linn tonearm. (I only did this as a stopgap until my new Linn armboard came that was pre-drilled for the Rega tonearm by the way)
I think the two are different by 7 mm or so and the Linn arm hole is larger.
I moved the Rega tonearm around in the larger Linn armboard hole until I was about 3 to 4 mm off. Then set the overhang so that it hit both marks and to my surprise it played just fine.
No inner groove distortion, no odd sounding bass or high or mids or anything out of the ordinary.
About 2 days later my new armboard arrived and I quickly replaced armboards and set up my table again. I can't say that I heard any difference at all.