The SME alignment tool does get things pretty close. And I agree a more fine grained tool gets better, and more repeatable results that can take your cartridge beyond what is possible with the SME jig.
Wally Malewicz of Wally Tractor fame makes the suggestion to enlarge ever so slightly the SME's cartridge mounting holes using a 2.8mm or 7/64 drill bit. Use a nice sharp drill bit turned into the existing holes. I was able to do this turning the bit by hand - the metal (magnesium?) is fairly soft. This allows the cartridge to be twisted a teeny amount to get better alignment of the cantilever with the line on the mirrored surface. A mirrored tool with a thin line works great - ideally one not wider than the cantilever. Really paid off for me with a SME Vd and Shelter 901.
Wally Malewicz of Wally Tractor fame makes the suggestion to enlarge ever so slightly the SME's cartridge mounting holes using a 2.8mm or 7/64 drill bit. Use a nice sharp drill bit turned into the existing holes. I was able to do this turning the bit by hand - the metal (magnesium?) is fairly soft. This allows the cartridge to be twisted a teeny amount to get better alignment of the cantilever with the line on the mirrored surface. A mirrored tool with a thin line works great - ideally one not wider than the cantilever. Really paid off for me with a SME Vd and Shelter 901.