Thanks for the info - your observations give me some faith I can pull it off. Would like to go that way due to a short time in Rome - would rather have fast than save a few Euro's.
I have perused the Trenitalia site as well as many other sites and posts and have seen conflicting information. As with many things Italian things can be confusing and contradictory as well as changing according to mood and interpretation. My Italian is progressing enough that I may try a direct call to inquire (and often one can talk to an English speaker anyway).