The effective length of a SME3012 version I &II is always a myth. If you Google this, I am sure there will be quite a few answers.
Since there is no easy way to find the RIGHT distance, I just did a rather scientific way of measure MY SME3012 V2.
So, by using professional Protractor, my is under Baerwald Geometry. Then, with the ruler provided, I rest it down on the locking hole using to measure effective length, of any tonearm, from 270-305mm. While there is a measuring pin at the other end, I carefully rest the point on top the pivot center.
A clear set up of a measuring ruler on a protractor.
Surprisingly, the reading on the ruler said the effective length of my SME3012 tonearm is 299.5mm.
In order to confirm this reading is correct, I have checked the alignment of my STYLUS (not the housing of the cartridge, on the Point A and C scales.
As you can see, both alignments on Point A & C looked good to me.
Okay, visual checking is done now, but since we are all audiophiles, ear checking is always more reliable. I will update my conclusion soon.