Koetsu cartridges - what arms work?

I have the new VPI prime scout. 
JMW 9 unipivot arm. Sounds sublime. 

Does anyone know if this is technically a match? 

Why not take an empirical approach, begin with a low mass arm, and measure the cartridge/arm resonant frequency, and add mass to the arm as needed until you hit the optimal range of 9Hz to 10Hz?

@johnhaines

I never forgot that Koetsu midrange . I am wondering about the arm match. I certainly will not back cue or scratch, it’s just for playback. I do want the ability to swap headshells.

Much like David Mancuso (RIP) who DJ’ed with pair of Koetsu. Are you gonna use two? Where on earth you have a place to spin records on public with set up deserved Koetsu quality (apms, speakers etc), in Japan?

So far the best tonearm (especially, but not only for Koetsu)
is the ViV Rigid Float.

In my system this beast has beaten all conventional tonearms
so far including classic 12", DaVinci, Graham, Reed and others.

idl57, It's not surprising that the Koetsu tonearm did not float your boat. Upon close inspection of photos, it appears to be a Jelco tonearm in Koetsu guise, which of course raises its cost by a factor of 2 or 3 compared to a Jelco 750.  Not that Jelco tonearms are "bad" per se.  

racedoc,  Can you say more about the Viv?  I was in Tokyo a year ago and lingered in Yodibashi Camera in Akihabara for more than an hour deciding whether or not to buy a Viv.  They had all 3 sizes on display (7, 9, and 14-inch)  Which do you have? I calculated that tracking error goes down significantly when you go from 7 to 9 but from there going to 14 doesn't help enough to warrant the extra length, possible issues with resonance, and the difficulty in mounting.  I would have bought the 9-inch, had I gone ahead with purchase.  My interest in the Viv is based on my own home experience with one of the only other "underhung" tonearms on the market, the RS Labs RS-A1.  That tonearm is also more excellent than one would want to believe it is by just looking at it.  This led me to believe that underhang is a serious alternative, that tracking angle error is not such a big deal (because both underhung tonearms develop a lot of tracking angle error as they traverse the LP surface, more than with any overhung tonearm).  By inference, this also suggests that headshell offset angle IS detrimental to maximum fidelity. (For others, the headshell on an underhung tonearm is not offset at an angle to the arm wand.)