It's going to take a lot of playing for me to get my ranking that high, I think. Once you're at this level, you have to win each of the three games in a match pretty decidedly. If you play a one-game match or a three-game match, even if you win every point, you'll go negative. If, in a five-game match, you lose a game, you'll go negative. If you win every point in two games but go to a long deuce in the third game, you might still go negative a few points.
I think I'll set a goal for myself of reaching 2400. We'll see if this happens. I did a little searching but couldn't find a Wii Tennis high-score list anywhere. Anyone heard of rankings over 2500?