With same PS distance you can use 3 different alignmet methods by moving/twisting a cartridge in the headshell slots.
Feickert protractor will give you Stevenson, Baerwald or Loefgren. Read more
here.
With FR7 series or SPU you have to stick to the manufacturer’s method, for IKEDA it is Stevenson, you can’t twist your cartridge, because they are headshell integrated models, so any other alignment will be wrong for those types (headshell integrated models).
Some protractors are made only for one specific tonearm and you can’t use them for any other tonearm.
Feickert designed for any tonearm, you can use it on any turntable and any tonearm and it's up to you which alignment method you want to use (Stevenson, Baerwald or Lofgren).
The
Dennesen is a protractor, not alignment, the alignment is Baerwald
Denessen U.S.patent number 4,295,277 cites Baerwald (not Stevenson)