@jw944ts , that is exactly how you tune the arm, by adjusting the mass at the cartridge end. Soundsmith has a very nice set of graded cartridge screws. If the resonance frequency is too high you add mass until you get it down to between 8 and 12 Hz. If too high you have to subtract mass. It is easy to add mass to a light tonearm but very difficult to subtract mass from a heavy one. You need a test record with resonance tracks to do this. Trying to calculate the required effective mass is almost meaningless as specs can be off enough to invalidate the math. It is always best to test the arm and find out exactly what it is doing.
Tonearm effective mass
I have read about and think I have a basic understanding of matching cartridge compliance and tonearm effective mass. I also have read a bit about how effective mass relates to moment of inertia, and how one can alter this by different combinations of counterweight/pivot point distance. What I havent seen, and I would think would be easier, is the effect of adding extra weight, ie heavier screws, in attaching the cartridge to the headshell...would this not, as well, increase the effective mass/moment of inertia? .help in understanding this would be appreciated...thank you