Who are some of the best fighters who regularly switched stances, i.e. going from orthodox to southpaw, and back again?
Hagler is the most obvious one, but Kid Gavilan also switched to southpaw in some of his fights which are on film, sometimes for an entire round at a time. DeGale has done it a fair amount amongst more recent fighters.
James Toney did it very subtlety. Watch his KO's against Nunn and Robinson. He throws a right hand from his conventional stance and steps through and follows with a left from the southpaw stance. He wouldn't stay southpaw for long but would use it when he needed to especially against a southpaw fighter. My old coach always told me the point of switching your stance is to throw punches from different angles and not stay there. If you stay in your unnatural stance for to long you put yourself at a disadvantage.
Roy and Mosley are a stretch IMO. I dont think they spent more than 15 minutes their entire careers actually in a southlaw stance. Giovani Segura is a guy who switched a ton
Johnny Bumphus did this. I think Jackie Beard too. A lot of the 1980-84 era U.S. Olympians/hopefuls were taught to do this and carried it, to some degree, into the pro ranks.
Prince Naseem Junior Witter With varying degrees of success Fury has done it sometimes - even fought a full fight early in his career VS Martin Rogan as a south paw
The straight or overhand right followed by a step through to left uppercut to jaw or solar plexus is the Fitzsimmons shift. Duran would do it very well, but yeah, Toney did it very well, when he did do it