How do they size up to say Maxxis new sizes Ardent etc or Conti Rubber Qs and Mtn Kings? Not sure if a 2.4 is going to be too big.

I have a 2.4 RQ on an on-one reetard and a 2.35 Fat Albert on a 521. I would say that they're prety much the same size – the Fat Albert looks a little looks bigger, but it's on a wider rim. That said, I like the Rubber Queen more than the Fat Albert (FA seems more like a rear tyre tread pattern to me, and didn't give a great deal of confidence in the front end when I rode it), but the Fat Albert is the older type, not the Carlos Fandango model.

I'd say 2.4 Nic and 2.4 Mountain King are about the same size, the Nic might be a tiny bit bigger.

However, a 2.2 RQ is bigger than a 2.25 Nic.