The Shure SFG-2 is definitely not accurate. But I still have mine and keep as a nostalgia collectable. Same with my original Discwasher.
I tend to believe the best electronic stylus force gauge is from Rega. However, they are very expensive. You can get basically the same results with the Riverstone stylus force gauge. They sell for about $35. This gauge is done right by measuring the stylus force at record level. As mentioned, some records are thicker than others. This gauge is based on the average of record thicknesses. From there you can tune by ear if you feel that is necessary. The Riverstone is a very good stylus force gauge and highly recommended.
I tend to believe the best electronic stylus force gauge is from Rega. However, they are very expensive. You can get basically the same results with the Riverstone stylus force gauge. They sell for about $35. This gauge is done right by measuring the stylus force at record level. As mentioned, some records are thicker than others. This gauge is based on the average of record thicknesses. From there you can tune by ear if you feel that is necessary. The Riverstone is a very good stylus force gauge and highly recommended.