Originally Posted by alcanoe

He doesn't have a triple with a 22 small ring (22/36/46). A major function of the rear derailleur is to maintain chain tension. The rings play an important role in determining the need for a long-cage mountain bike RD.

Cross shifting is no additional problem (not a good idea in general) as the chain should be sized big enough so it fits the big ring and the big cog, otherwise you'll brake the chain if your forget. Small ring (22) to small cog (11 or 12) will cause the chain to rub on itself at the jockey wheels even with a long cage RD. That makes a noise which tells you that you are crossed, but it causes no damage or problems.

Al