Heres an idea one might like to try out.

Betting 1 or 2 horses a race.
If it ran 3,4,5 last start , bet 3 units.
If it ran 6,7,8,9 last start , bet 2 units.
If it ran 0,1,2 last start , bet 1 unit.

The idea is to try to instill some value against the over bet horses that ran 0,1,2 last start.

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Cheers.