I have no idea if this would work but what if you did loss sharing? For example you got 4 horses your initially following call them Apple, Banana, Lemon and Melon. Apple is the first to run at $4 odds so you have to bet $3.33 to get your $10 profit, unfortunately Apple loses so you loss share:

The profit required on your next bets for all horses would be:

Apple: $10.83
Banana: $10.83
Lemon: $10.83
Melon: $10.83

(The $0.83 is from $3.33 / 4)

Next to run is Banana, follow the same process and so on. Like i've said I have no idea if this is actually viable or would work but my logical thinking is that even if 1 horse just doesn't seem to perform at all and you don't get that win your chasing, then at least you've shared the losses across other horses that you'd hope eventually will lead to that win to offset the losses.

Has anyone trialed something similar to this previously? purely just an idea i've came up with sitting here at the moment.