Linear Tracker ...I was wondering

Actually,the best air bearing arm is the Walker. It had the lightest horizontal mass. The air bearing is stationary and large. It uses a lower pressure (less noise). The arm is made out of some type of very light composite. The turntable section is actually the original Air Force, air bearing platter, air bearing suspension etc.  https://walkeraudio.com/proscenium-black-diamond-v/
Unfortunately, Walker also sells a bunch of BS on their web site and I refuse to support that. I find it odd that the press has not compared the Black Diamond to the Air Force 1.

Surprised there is no mention of Advanced Analog MG1. An affordable linear tracking option. Their site is under construction. But there is info there.

adanalog.com

How accurately and repeatably can one set azimuth on the Walker? Looks like a simple collar-and-tube system, which is not really either. Do you know, Mijo? 

OP, have you noticed how the discussion has progressed to the point where we are now discussing the merits of the tonearm on a $150,000 table, or the legendary ET, compared to the Trans-Fi?

mijostyn - do you have any idea how many times you have used the word "Horizontal Mass" on this thread alone.

"I won't even look at an air bearing arm because of the problem of too much horizontal mass."

Then, why are you posting here still ? 

FYI ..............et al 

Cartridges mounted on an ET 2 do not see the Horizontal Mass due to the patented I Beam/Counterweight design. A vertical leaf (flat) spring isolates the counterweights from the air bearing spindle. If interested to learn, it makes more sense, I think,  for you to do some research, download the manual, and come back with any questions if you have any..

I have used 50 Sonus Blue Gold 50x10-6cm/Dyne on the ET 2
with no problems whatsoever.