Here's the email I got from Ken..... for all the other SME owners out there.
"I'm assuming the SME III uses the typical SME adjustable base mount. Does it also have slots in the headshell? If it does, I need to know what mounting distance you want to use. If it does not, I would not recommend using this type of protractor. I'd stick with whatever SME provides for it. The reason is that if the headshell does not have slots, the effective length (mounting distance plus overhang) cannot be adjusted for different cartridges. The effective length of the arm changes with every different cartridge that is used in it because there is no standard for the location of the stylus in relation to the location of the mounting screws. The accuracy of the alignment using this protractor is completely dependent on the mounting distance. Every mounting distance has a unique overhang and effective length associated with it. If the headshell has no slots, the cartridge cannot be moved in the headshell to compensate for the longer or shorter cantilever length. If the cartridge is in a fixed position, but the cantilever length changes, this changes the position of the stylus which changes the effective length. Since every effective length has a unique mounting distance associated with it, changing the effective length requires a different mounting distance. It would be easy enough to move the base of the SME arm to a different mounting distance, but then a different offset angle is required. If the cartridge is fixed in the headshell, the offset angle is also fixed."
"I'm assuming the SME III uses the typical SME adjustable base mount. Does it also have slots in the headshell? If it does, I need to know what mounting distance you want to use. If it does not, I would not recommend using this type of protractor. I'd stick with whatever SME provides for it. The reason is that if the headshell does not have slots, the effective length (mounting distance plus overhang) cannot be adjusted for different cartridges. The effective length of the arm changes with every different cartridge that is used in it because there is no standard for the location of the stylus in relation to the location of the mounting screws. The accuracy of the alignment using this protractor is completely dependent on the mounting distance. Every mounting distance has a unique overhang and effective length associated with it. If the headshell has no slots, the cartridge cannot be moved in the headshell to compensate for the longer or shorter cantilever length. If the cartridge is in a fixed position, but the cantilever length changes, this changes the position of the stylus which changes the effective length. Since every effective length has a unique mounting distance associated with it, changing the effective length requires a different mounting distance. It would be easy enough to move the base of the SME arm to a different mounting distance, but then a different offset angle is required. If the cartridge is fixed in the headshell, the offset angle is also fixed."