Leave 14 tooth on the front
40 or 42 on the rear for improved acceleration (needs a longer chain though 96 links I think)
For the cost, it may be worth considering a quick change carrier
Changing them over is easy enough, and I used the instructions here
I'd recommend reading it through first though, as the allen key needed to remove the cush rubbers isn't mentioned in the tool list (12mm IIRC)
http://www.ducati.ms/ubbthreads/down...ch_id=177?Cat= Jason