SL-1200G/Hana ML Best Headshell

I have read that the technics  arm was tested to have a 9g effective mass.  

the stock headshell has a lighter mass than most if not all aftermarket head shells, something i have found valuable trying to match cartridges.  

another plus for the stock headshell is that it has a low cartridge mounting surface.  most aftermarket headshells have a higher cartridge mounting surface.  this could prevent setting a level cartridge and proper VTA because the arm height adjuster runs out of travel resulting in too much tail up.  

this would mean using a much thicker mat or cartridge shims.  

No, the Technics SL1200 tonearm has an effective mass of 12g

The OEM headshell is 7.6g. 

From the HiFi News test report-

OK, I thought we were talking about the SL 1200G. I bought my 1200G shortly
after they came out. I did the research and the consensus was that the tonearm
mass was 12g. I found this information from several sources. I don't have the
time now to do the research again.

Also, the article above refers to the 1200GR. My understanding is that the 
GR has an aluminum tonearm versus magnesium for the 1200G.

Think of it this way: square root of 9 is 3. Square root of 12 is ~3.4. So the difference between 9g and 12g is not going to affect the calculation of Fr by much.