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.  

From the HiFi News test report-

The tested effective mass of the GR tonearm is the best actual data I have seen for this spec and the G arm should be very close to this number. 

Effective mass as spec'd for tonearms is a qualification of its inertia or resistance to motion, not the weight of the arm wand.  The most influential properties that affect the inertia are headshell mass (same for G and GR),  distance from headshell to pivot (same), counterweight mass (same) and distance from counterweight to pivot (same).  Bearing friction is also a factor and assumed to be the same. 

The Gs arm wand is made of magnesium which is lighter than aluminum but again not much of a factor in calculating effective mass.  The EM of the GR and G should be nearly identical.