I have not seen this posted elsewhere. Not my thing, no affiliation but with my satisfaction with my 6XC II set-up if I was contemplating a bigger cartridge I would be all over this.
http://www.davidtubb.com/index.php?route=product/product&product_id=180&search=brass
http://www.davidtubb.com/index.php?route=product/product&product_id=180&search=brass