You may need to consider a better way to rank players - percentage of games won is problematic (as was discovered during the Tron Google AI challenge) and something like TrueSkill or bayeselo would be more robust.
Easiest thing to throw together now is a script which just feeds the whole game history into bayeselo as a bunch of fake chess matches, with the white move advantage set to 0. That's what was done for Tron.