Yes that is correct, all of the ball diffs here came with two shims also, the setup will really depend on driving style and which car. On the HT carpet here I have tried it with two and also with one shim. I like the feel with one shim but you loose some forward bite so I've stayed with two on both of my cars. I have'nt tried it with the three shims so I cannot comment on that.
While we're on the subject has anyone tried the atomic ball diff? I bought one to try and cannot seem to get it to work well at all, and the gear doesent fit well either. I was thinking of replacing the gear with a standard Kyosho one but the balls are a different size
. Any tricks or tips on a good way to rebuild this for a better feel/fit?