I owned several Koetsu cartridges. Onyx Platinum, Coralstone Platinum and now the Coralstone Diamond Cantilever Platinum. I've not tried the Koetsu on the Kuzma 4pt tonearm although I have a Kuzma 4pt (11") but not setup yet. I've got 6 tonearms including the Kuzma and that's waiting on another turntable to be setup etc...
Anyway, 2 points:
1) I would recommend that you try the Koetsu stone body carts. Much better than than the wood bodies. Especially given your choice of TT and arm. In fact, I would urge you to try the Diamond cantilever stone bodies.
2) One of my turntable dealer friends have tried the Koetsu Coralstone on the Kuzma and says it's a good match. I don't doubt him as he truly knows turntables and owns both Walker and Kuzma.
Best