Dear @chakster : Own geometry? where do you read that or whom tell you?. Sony is a japanese manufacturer and used Stevenson A alignment. There is no " dedicated " protractor for it, the one you have is a protractor where the manufacturer gaves to the customers but northing special.
Stevenson A is what you have there.
Again, I know you are not stupid but only with high ignorance level on that regards and because you are not stupid you always can learn. So do it !
Btw, which kind of question is that: " ave you ever read Stevenson’s explanation about his method ? """
please learn for you can’t make any more that kind of questions. If you don’t learn then you will cross that line of stupidity where some person here belongs. Take advantage that you are no there yet and do it a favor and learn or look for a good advisor/mentor/teacher in that alignment regards. I’m sure you can learn.
The only special-dedicated tonearm geometry/protractor I know is that one by SAT tonearm and with out any explanation yet by the manufacturer that alignment design was made it by ignorance.
@lewm, there are no " secrets " ( as you could think. ) about tonearm alignment subject only marketing that is bougth by people with not the rigth knowledge level on that regards.
You can use the 247mm/250mm Löfgren A/Baerwald on your tonearm with great success and better on what you have now, using the parameters I posted here somewhere. Even the ivelchev that's Löfgren A choice works just fine. Anything but Stevenson A !. At least you can try and if you don't like it just comeback.
R.