As I remember (AirChina, Kalitta, and others) the 747 tends to shed outer panels of stab/elevators and gear doors with Mach+ excursions.
Not a regime that I'd ever want to explore.
Then the 747SP's were certified (as I remember) even faster than normal 747's? Maybe they operated faster, sorry, can't remember.
Do I remember that an elevator or a piece of one was recovered in the AF447 debris?