Koetsu cartridges - what arms work?

@lewm 
The skating force changes the direction using the ViV Rigid Float.

At the "lead-in groove" (the start of an LP) there is a very weak
force to the inside.
Most of the part of an LP there is no noticable force (even with a
flat / non-grooved platter no movement).
At the "lead-out groove" (the end of an LP) there is a very weak
force towards the outside.

In average the skating force is negligible compared to a "normal"
tonearm.

I have heard many fine systems utilizing Koetsu cartridges, but, I cannot say to what extent the particular tonearm contributed to, or detracted from, the sound I heard.  A local dealer that is particularly fond of Koetsu cartridges likes the Ortofon RS-309D tonearm (12" tonearm that can accommodate a SPU-type headshell).   

I have been using a Koetsu black on a Fidelity research FR64 arm and highly delighted for the last 20 years.

 Racedoc, did you actually make quantitative measurements of skating force? Or are you reporting your observation of what the tonearm does on a grooveless LP? In any case the skating force will be a function of the friction of the stylus in the groove and the angle of tracking error. There’s no getting away from the calculation. I do question the importance of skating force generated by by tracking angle error.  The possible benefit of an underhung tonearm like the viv float is that there is no headshell offset angle which also generates a skating force that is additive with tracking angle error, at points on the LP where the cantilever is not tangent to the groove. And by the way examining skating force on a grooveless LP is fraught with sources for error. There is much less friction on a grooveless LP for one thing. 

Finally, I am not sure I understand your first sentence where you say that the skating force changes direction with the viv float. Can you explain further?

Fidelity Research FR64s - excellent combination with my Urushi Vermilion.