carryon plus a backpack?


No.
Your carryon allowance is one bag. A backpack is also a bag.

My opinion...it's too large, especially if it's going to be packed full. Not worth the hassle...take a 22" if possible.

A 24" expandable rolling suitcase( expandable feature only used on the way home) is perfect for me. I check it thru on planes, but it is easy enough to deal with myself on trains. A 19-22" is just a little too stingy for my packing style. Packed weight is 25-30 lbs.


fabrizio~ 27" is still awfully large and certainly not allowed as carry-on for flights. You probably would be able to manage it thru train stations, depending how heavy it is. IF you are a habitual overpacker, I doubt you can do a trip in a 21" only. Packing light is a learned skill in my experience. Baby steps... at least aim for one small rolling suitcase but knowing you'll likely check it on planes.