Hi Oz,

To my way of thinking the 3 primary handicapping factors are Speed, Pace and Class.
The use of Sectionals helps us deal with finding Speed, Speed at the right time, is a function of Class.
One of the problems with trying to HANDICAP TIME/SPEED factors is the presence of races of different distances in the past performances lines of runners, and/or race results from other tracks. In order to overcome this deficiency, one needs to use track records and Par Times for all the different distances , then using those, and the past History of Winners and using simultaneous equations you can create a model of a race winner in terms of change in SPEED relative to the parts of a race.
Your next step would be to look at how to get rid of the initial acceleration portion of a race so you can complete the other important computations

On another note in your calculations I would use (race winners timeX Race distance)/ actual time of other runner) that will provide you with the distnace completed when the winner crossed the line.