Vig,

although you've managed to figure out that the other methods are unsuitable, why do you insist on ignoring my method which clearly works and I believe is the only practical approach?

Now, much as I despise Z-scores they do contain some theoretical beauty.

Woof appears to be the only one besides me who realises that Z-scores CAN be used to calculate the probability that A beats B. If A and B are Normal, then so is "A-B", the distribution of every possible matchup of A vs B.

Trouble is I believe it's highly unlikely in typically chaotic races that ratings are Normal.