Chrome,

If you still want Don's approach even though, as you say it, "did indeed fall over somewhat", then all I have to do is understand what part\parts you need.

I mean his first breakthrough came when 50 years ago he realized that;

Instead of comparing one horse against another, he would simply compare it
with an imaginary average horse carrying the limit weight in an average race -
and provided that he knew the class of that race, and the difference between that class and the class of every other race, he was on his way.

Using the handicapper's theoretical weights as a basis he worked out the weight difference between (in those days) a maiden - novice - encourage - graduation -welter - open. Once he had established these diffs. he found there was a simple method of rating every horse and used it successfully for 23 years in conjunction with his pricing for profit using his ratings.

You must say if that's all you need Chrome, or if you need his method of rating the performance of a horse in a race ?
I don't want to be typing away unless you want more.

Regards.