I can't speak to the "R" but I've owned a Kuzma Reference and still use an XL, which has a bonded fabric mat of some sort. My suggestion is to talk to Franc and to Scot Markwell (if you are in the States, he is the U.S. distributor). Both may have ideas to help you, though presumably chose the mat that came with the table for good reason.
I did change out the factory clamp on the XL for the Stillpoints record weight a number of years ago. I find it more "pacific"-- there was an upper bass bump using the factory clamp that gave a propulsive aspect to the sound. Compared to the Stillpoints, less prominent bass, more relaxed sound. I adjusted other parameters, including the woofers, to accommodate the clamp change. I've gone back and compared factory to Stillpoints a few times since and still prefer it to the factory clamp.
Franc does make an ebony record weight which I haven't tried. Not as crazy expensive as the Shun Mook but still pricey.
Good luck, Franc does nice work, is a nice man and I've found his support for the products to be second to none. If I ever get to Slovenia, I'm gonna visit him.