I agree becareful,
The point is a rigid set of rules won't work, you must be flexible and constantly able to adjust for the circumstances.
This does not mean historical data is useless, it is in fact very helpful and a good pointer to the future. But even if it were possible to run a race of exactly the same field under the exact same conditions it doesn't mean the same horse would win.
When you get your head around that you will be on the right path. I Hope!

Another thought on systems- the marginal selections, when back checking you kno the results and therefore will probably include the winners and leave out the losers, will this happen when you have to put your dollars down?

I will have more to say about this in the future.