Shaun,

You could think of multiplying the horse's API by it's win% or it's place%. Perhaps the place% because history suggests it seems to be a slightly better indication of how the horse is going to go today than the win%.

But yes Mo, I think the API is a good thing to use. Thank you for pointing out that it was on that website because I didn't know that. I actually don't have any systems relating to it, but I might have to have a look at it.