I would like the Mezzo to be go any where bike so a wide range of gearing is what I am looking for. The chain guard on I4 is quite small so it wont take many more teeth than 42 so I will have to change that as well. The crank on my I4 is SR Suntour but most of the D9s I have seen use a Truvativ crank, don't know why they fit different cranks unless its to do with the pcd. From my measurements the I4 pcd is 130m, perhaps the 54 chainring is only available in a larger pcd, need to do more research.