A four-stone handicap is not small: a beginning professional player could give any top Go player (there are several major championships) a run for his money with 4 stones.
Just to clarify: a beginning professional player (as in, a player who is considered of professional rank in the Go world, but just in the beginning of their career) will beat any top Go player with 99%+ certainty at 4 stones. The difference between professional players are far less than 4 stones.
If you meant a student studying to be a professional, then 4 stones would probably be true for an even chance game.
