Currently I'm using the average ground gained or lost from the horses' starting post to call at the half.
Typically 4 or 5 starts.
So a change from post 8 to 2nd would be +6, a change of post 3 to 8th at the 1/2 would be -5. Averages above 2.5 I call a Leaver, below -2.5 a Closer and in between a Stalker.
If an outside horse is the sole leaver in the race that's a plus. If there's 2 or 3 'Leavers' inside him he's almost a write-off.
I've thought about using a 'Half pole' Speed rating using leaders time, lengths back and adjustments for post start, ITV and DTV. In fact, my program does that but I've never got around to testing it.
You might check.
http://www.paceadvantage.com/forum/s...d.php?t=138917