I got some nice road rash once when a sewup-err-tubular rolled off my rim in hot weather flying down a grade going 50MPH+ (hey, thats what the guy in the car behind me said I was doing. I lived where it was usually cool, so generally used the gummy tubular glue (Mastik or something?), and not the dry hard stuff (Clemenit?), because it made it easier to swap a flat tire.
Sewups-er-tubulars were wonderful riding, but I switched to 700c clinchers in the mid 80s, and haven't looked back