Sylvia,
thanks for the link, very helpful.

Regarding the size of this carry on, you might get problems. US airlines are not (yet) very strict. LH is very strict. And when you pass FRA the airport people may trouble you.
I have a similar bag:
-LH did not let me take it as carry on.
-Delta did, however, the plane was so full, no place for the bag. Delta was prepared: a service man checked it in at the front door of the plane.
-Some overhead boxes (like on some 747-200) are to small for such bags.