Hi,
I think this is simple, but maybe not:
1. For races with volume > V (e.g. 2,000)
2. Dutch a number of favourites up to p% (Back Book% from Top < P%), say 70%
3. If wins = 0 (last race was a loss) then bet to win an initial amount, say $10
4. If wins > 0 then increase the last amount to win by N%, say 10%.
So the first race dutches to win $10. If it wins, the next race dutches to win $10*(1+10%) = $11. If it wins, the next race dutches to win $11* (1+10%) = $12.10. And so on until there is a loss, then start over at $10.
Thank you