You may like to try this.

1)Only back those selections of yours if the whole field has had 2+ career starts.
2)Only back your selections if they are paying $3.30+ at jump time.

Staking
Bet to win a fixed 5% of bank using a Min divisor of 3/1 & a Max divisor or 6/1 so as to get any overs.
We do not try & recoup losses from the past races.

E.G. Bank is say $200 @ 5%=$10 Target say its price is $3.40 ,the min div is 3 ,so we place $3.00 on it , & it looses,
Next race price is showing $8.90 ,we Target $10 divided by the max divisor of 6=$2
It WINS ,return $17.80
Total O/L $3+2=5

Our target in this exercise will be $10 for each race ,not adding losses.

If you feel you know when to stop on a bad run of outs ,say 10 in a row then start again once a winner gets up,using a progressive plan so as to recover all losses, I would target to win no more than 1% E.g.$200 bank is $2.00
Using the same Min & Max divisors.

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Cheers.