I am embarking on my first trip to Italy and working to firm up my itinerary. I am flying into Venice and out of Rome. I am starting with friends for three days/nights in Venice, two days/nights in Florence, and then on to the Cinque Terre. I would like to visit Siena on my way to Rome. Once I leave Cinque Terre I will be on my own until Rome. I'm trying to decide if two nights in Cinque Terre with one full and two partial days before traveling to Siena, then two nights and a full day in Siena before going to Rome makes sense. That will leave me three nights and two full days in Rome, plus partial days on arrival/departure. I adapted this from the "three weeks in Italy" itinerary in Rick Steves Italy 2017.
I am not sure if it would make sense to just spend one night in Siena and add another night to Rome, or otherwise. Any recommendations or modifications anyone would suggest?