My father, is a natural lefty, but learned the game as a righty. Not an avid golfer, he never carried a handicap, so I don't know what his "best" golf was. He switched to his natural left side when he was about 50 years of age. The swing was more fluid and had better rhythm from his left side. My son putts left handed and swings right handed. My advice would be that it would be a difficult transition, but remember it is a "stick and ball" game, like baseball, and there are a lot of switch hitters in baseball, so it can be done. But, most switch hitters hit better from one side than from the other.