The Schick arm is by far the favorite choice amongst my customers for the OMA slate plinths for the 301 and 401.
I've had a very wide variety of arms requested for the OMA plinths for the 301, including Schroeder's, Da Vinci, and TriPlanar, but the Schick is definitely the most requested.
Disclaimer- I sell the Schick in North America, and make slate plinths for the Garrards.