By George:
Captain 'Hoot' Gibson of TWA 727 fame, is the man to ask about flaps at high altitude. I think it's called, 'the other way to get down'.
He certaintly is. He would refer you to Boeing and today probably cite the 787 as an example of Boeing's methods.
As a fellow TWA pilot may I add, as I have before, neither the FAA nor the company faulted that crew. The NTSB did because they were in Boeing's pocket at the time.
Now, many years later, the FAA is in Boeing's pocket instead of the NTSB.