I’m not suggesting the Feikert is the best. But it’s worked well for me.
I agree but for the Feickert and Dennesen to work you have to be able to accurately locate the exact centre of the horizontal tonearm bearing and this is often not possible. Some arms now have a locating dimple for that purpose.
If you can't find the centre of the horizontal pivot bearing the traditional 2 point protractor will be far more accurate.
I have both the Feickert and Dennison and I have gone back to 2 point protractor with a pin prick in the card to locate the stylus. It is more fiddly but more accurate than the F&D, assuming the 2 point protractor is correctly manufactured to spec.
The 2 point protractor I use has very fine lines compared to many others - this too is important for accuracy.