Keep in mind that the cartridge is "NOS", which literally means new OLD stock. So for one thing the compliance may no longer be what Ortofon said it was 20 or 30 years ago (or however long ago the thing was built). Moreover, that equation is flawed in many ways in terms of its ability to predict reality. In sum, your results do not surprise me. But at 6 Hz resonance, I am a little bit surprised that it is so sensitive to footfalls. You might try isolating your table a bit better. (I bet you hoped no one would say that.) I have one of these, also purchased from Thakker. I am using it in a Dynavector DV505 with its 11.2 gm headshell, which darn near must approximate the effective mass, since the rest of the vertical pivoting arm is so vestigial. So, not too different from your setup in terms of the parameters. I am having no problems with footfalls, on a Lenco in a heavy but totally unsuspended slate plinth. I have no idea what this means, but maybe it helps you.
I just thought of one more thing. Over on the VA, some experts have noted just in the last day or two that the HFN test LP is very inaccurate in that the actual frequencies recorded are not as labeled, another source of error. The Cardas LP is recommended as being more accurate.
I just thought of one more thing. Over on the VA, some experts have noted just in the last day or two that the HFN test LP is very inaccurate in that the actual frequencies recorded are not as labeled, another source of error. The Cardas LP is recommended as being more accurate.