Paul Elvstrom's most mentioned accomplishment is his four Olympic Gold Medals. However, to my mind, Elvstrom's greater accomplishment was winning both the Finn World Championship (Finn Gold Cup, 1958 and 1959) as a skipper and also the 1962 Flying Dutchman World Champion as a trapeze crew (Olympic performance double-hander at the time). There is no better example of Elvstrom's greatness than being the top skipper in the most competitive singlehander class of his era and the top crew in the most competitive trapeze class of his era.
Paul Elvstrom's experience as a trapeze crew led him to develop the first trapeze singlehander class (named, what else, the Trapez) which he introduced at the 1965 singlehander trials in Weymouth, England.
1962 Flying Dutchman Worlds - St. Petersburg Florida - Hans Fogh skipper
You would think winning a Finn Gold Cup and then turning around and winning a World Championship as a trapeze crew would be unique in sailboat racing but it turns out the accomplishment was repeated - by an American. Cam Lewis won the Finn World Cup (1979 and 1980) and was also winning trapeze crew at the 505 Worlds (1981 and 1982 - twice, for two different skippers). I would think with the increasing specialization in training for the Olympic classes that we will not see anyone else join this exclusive "double skipper/crew championship" club.
Cam Lewis in his Finn.