Seeking arm suggestions for a Grace F9R

Robbie, No problem about misspelling my moniker.

The range of acceptable resonant frequency is generally taken to be 8 to 12 Hz, not 10 Hz on the nose.  We'd be going even more nuts, if we sought an exact 10 Hz.  At 7 Hz, I repeat, do you have a perceptible problem? Speaking of footfalls, if you know anyone who tap dances at 7 Hz (that's "cycles per second"), he ought to be in a Broadway show.  The only way you'll hear an improvement, if you change tonearms to achieve 10Hz (or the acceptable range of 8 to 12 Hz), is if the new tonearm is simply superior to what you are using now.  

So, if you are estimating RF with a test LP, then you have an equation with two unknowns (Compliance and Effective Mass, but maybe not, if SS gave you a figure for compliance).  Assuming C and M are not exactly known, how are you going to calculate exactly what Effective Mass will move the RF up to 10 Hz?  Like I said, it ain't worth the trouble.  Also, because RF is inversely proportional to the square root of the product of C times M, it may require a very light tonearm to move RF from 7 to 10 Hz.  It's "LewM", by the way.

Robbie, Did you actually measure a resonant frequency of 7 Hz, or did you calculate it based on assumptions of compliance and effective mass?  If the latter, and especially if you're really not having an audible problem with bass reproduction, I would say forgeddaboudit.  This business of worrying about resonant frequency is one of the most over-rated in vinyl world. FWIW, I run my Grace Ruby re-tipped by SS in a Dynavector DV505 with original DV headshell.  Like Dave says, it's a great cartridge.