Blackbird / SME

Viridian, the effective mass of the detachable head shell version is 12.5 gms. This version is 9.5 grams not 6.5. There is absolutely nothing wrong with that vertical bearing it is just expensive to make. Every arm has some "secondary" resonances the better tonearms are usually well dampened as I am sure the SME is. The Blackbird has a compliance of 12 X 10 -6 cm/dyn which is on the lowish side. This arm is a little light for this cartridge. The detachable shell version would have been a better match but that can be fixed with a little added weight and a test record.

The resonance frequency with that arm and cartridge is 11.27 HZ. Those numbers are damn good! Why would you need a headshell weight?

You might look @ some of the high compliance models offered by Soundsmith. They have a few models in the $500-$1000 range.

DeKay

Viridian I would tend to trust SME's specs more than Analog Classics
Chatter is a figment of some peoples minds for some reason. I doubt this can happen even with loose bearing races. Forget about tapping the arm tube. Tap the cartridge body. If that rings you have a problem. Yes, a stiff cartridge might reflect a little more energy but actually unless the cartridge body weights less than than the effective mass of the diamond and cantilever extraordinarily little energy is reflected back to the arm. In reality the effective mass of the diamond and cantilever are so low in a modern cartridge in relation to the mass of the cartridge I would be surprised if the arm see's any energy other than the linear force that moves the arm across the record. I love these myths perpetrated by people who think they know what they are talking about. Unfortunately, these myths frequently get wings because they seem to make sense.
Beware of people who seem to make sense. 
Viridian I am 65 and have own over twenty tonearms. I never bothered to count and at least twice as many cartridges all the way back to 1965. 
OK Viridian now it is your turn. Prove to us that a tonearm can chatter and we want to know exactly how you determined this and we want to see the data.