The announcer states just before the first attempt with the final sling shot design that buster will experience between six and nine G's. Buster may experience that but the Apollo astronauts and the Space shuttle astronauts G load never exceeded 3 positive G's EVER. A rare mistake by the MythBusters.
During the slingshot section, the voiceover states that the fatal catapult that killed a student was situated in Oxfordshire, UK. Actually, the catapult was in Middlemoor Water Park near Bridgwater, Somerset - over 100 miles away. The confusion may come from the fact the man who died, Kostydin Yankov, was studying at Oxford University.