Subsonics with Grado & Rega Arm

I get massive amounts of subsonics with my Rega arm and Grado Reference cartridge.

Anyone else have the same problem? What arms would be a better match for the Grado Ref?
After doing some calculations the Grado cartridge resonance with the Rega arm is 8.4Hz.

When one takes into consideration the heavier after market counterweight I use the Frequency will drop even lower beacuse the arms effective mass will increase from 11 to lets say 13 or 14g.

What baffles me is that Grado suggested to me that effective mass arms between 12-16g are good with 14g being optimium.

One would think that a lighter arm would be a better match say around 9g and thus raising the frequency to between 11-12hz.

Bottom line Grado and Rega don't match on my table and I'll be trying another cartridge perhaps a Benz H2.

If anyone would like to comment further please do.
I am currently using a Grado Gold with a Expressimo modded
RB-300 on a Thorens 320 suspended turntable with very good
results.I'm suspicious that there is something else that
has not been investigated.Have you verified that all of your
wiring(low volt. vs. 120V) is truly isolated ?
I was having a similar problem. I have been using a Grado Reference Sonata with my Rega RB300 Origin Modified arm on a Sota Star Saphire table with the Sota Reflex clamp. I sent my arm to an Audiogoner (Michael Wharton - for rewiring the arm in Cardas and installing a Cardas 5 pin DIN termination. I purchased a custom tonearm cable from a terrific fellow in China that incorporates twisted pair construction of LC-OFC wiring with braided copper shielding, hermetically sealed insulation and an RF stopper - all for a very fair price and QUICK turnaround). The problem is completely resolved. I am hearing much deeper into the vinyl now even before any meaningful time for burn-in has occurred. I could not be more pleased. Actually, this is one time I can be the guy to say that he cannot believe the magnitude of improvement a tweek made.
Would a phono stage with subsonic filter help?
Grado dance and woofer pump when used on an old Thornes. I dont think Grados like suspension turntables. No dance on rega table but hum increases nearer to motor. I think Grado on Rega is very musical regardless of how the numbers crunch out.