You can add me to the list of non-believers too. As I recall, the max certificated altitude of a VC10 was 43,000ft. When I was a young pilot, the training captain I was flying with, took us up to a little over 46,000ft on a training flight at a reasonably light weight in smooth air and with a good horizon, to demonstrate the high and low speed buffets. There was a margin of only a few knots between the two and one had to be very delicate on the controls when edging towards each limit.
It was a non-standard exercise but taught me never to go there in rough weather. Limitations are there for a reason. Adding a margin in bad conditions is good airmanship.