... Do you know if the roll axis ring is just a commercial/industrial turntable bearing?...
Apologies for the delay in responding. I am out and about with intermittent internet access.
The roll bearing does look suspiciously like the McCarr item. As for the lack of shock absorbers etc., my belief is that the CW gimbal was designed before HD digital cameras were widely available. Tape based SD cameras are far more forgiving of vibration and do not produce the ghastly jello at the mere suggestion of vibes and furthermore, the SD image was soft enough that any mild HF vibration was not apparent anyway. As such, the gimbal was adequate. Nowadays though, the extremely sharp HD cameras demand that careful attention be paid to vibration elimination and perhaps an extra layer of isolation between airframe and gimbal booms would be advantageous. Most of the previously mentioned mods have been directed at vibration isolation.
As always, finding the balance between soft isolation, to eliminate vibes from reaching the camera plate, and rigidity to prevent the whole thing wallowing is a delicate one.
On such a helicopter you will rarely reach a state whereby everything is settled and no further work is required. IC engines are subject to all sorts of variables that will affect vibration frequencies, which in turn will reduce the effectiveness of specific frequency dampers. It is generally a constant work-in-progress but, if you need to haul around a heavy camera for nearly an hour there are few alternatives.