FWIW, the stone bodied Koetsus work well with the Kuzma Airline- it doesn’t have high vertical mass, but the horizontal mass is considerable (this, notwithstanding Franc’s claim that the air bearing is frictionless and makes that irrelevant for most purposes). I have a Jade and Tiger Eye, both new from factory. The Jade is very good; there is some criticism that it makes everything some the same- i.e., a coloration. The Tiger Eye, which took time to break in, has more high freq information, and I’ve been running that for a while.
These are special cartridges- normally a high mass arm of the old type is required. But the combo of air bearing linear tracker + Koetsu works magic in my system; it isn’t just midrange purity-- I’ve had Van den Hul, Lyras top offerings and Airtights- none had the bass dimension and tone of the Koetsu along with that magical midrange. 
