I know Rick advocates packing light. And after several journeys across Italy by train, understand and practice that concept... mostly.
But, I have to ask, why do you have to carry it on? Are you afraid of loosing your luggage?
Our first trip to Italy was 24 years ago. We flew into Venice - without either of our checked bags. We had an adventure right off the bat. Of course, we had not packed a change of clothes in our carry on!!! Only snacks and games and books for the flight! Ugh. Lessons learned!
We now remember to pack clothes in the carry on but still check bags (one each). It makes the airline/security routine easier and less stressed.
Not really looking for an answer - just the reasons why YOU choose to carry on only and then deal with one bag limits (what constitutes ONE bag on which airlines) liquid limits (3-1-1 rules) and hassling with those overheads on board the plane!
Maybe I'm just too old fashioned?