You can keep simple or sophisticated models.
To paraphrase something from the Follow Up, some people are comfortable juggling just a few factors -- like Early, Late and Total.
Others do well utilizing all the categories available -- like the information found on the Excel spreadsheets Richie and others have so generously provided.
No matter which way you prefer to model, I strongly suggest you avoid adding a race when any of these three conditions are present:
- "Muddy"
- "Yielding"
- "Fell" or "Lost Jockey"
If you include any of these races you'll wind up with an inferior model.
I'll leave "Sloppy" and "Good" to your discretion, but the jury is in on the above.
Case in point, if you added this double whammy to your model you'd surely be sacrificing a degree of accuracy.