becoming a championship boxer.....

[WhoIam]

Most championship boxers at the lower weight limits are just short and built like any other boxer. Despite his superior size and reach, your friend would get clobbered by some 5' guy. Also he would be about as threatening as Calista Flockhart and have absolutely no power behind his punches. His only chance at winning would be making his opponent laugh so hard he would be unable to get up.