Navy is 5-0 this year, but at least one of those was a close-call Northeastern, a div-II team. Navy has also beaten Duke, Tulsa, Air Force and Vanderbilt. They combined record of Navy's opponents in DIV IA contests is 5-16.
Notre Dame, while not fantastic, is a full step up in class versus Navy. ND-6x is not a bad play, but I'd be reluctant to lay 7, since Navy tends to play its best game of the year against ND.