Hi Bhagwan, I did a brief test on this (on paper) on Tuesday Races.
I left out Maiden races and only went on the others that had 9-13 starters.
The result i got wasn't brilliant Out $24 for Return of only $4.90 (2 winners from 9 races) BUT I did a comparison on the same races using top 5 API (suggested by LuckyBoy in another post), which gave a return of $22 from an outlay of $31. Not remarkable, people may say but if we had dutched them on an outlay of $10 per race the result was out $100 return $107. Still not a big deal but this was 4 winners paying $11.10/$2.10/$5.90/2.80 and there were quite a few bets on horses showing over $13.00 at the time.
(After looking back at the races 4 of them had 4 qualifiers so under the top 3 rule they would not have been eligible. Of those 4 races there was only the $2.10 winner therefore the real picture is much better.
i.e using the API for the TOP 3 the outlay would've been $19 and return $19.90 and dutching woul have been outlay $60 return $94.40).
Sorry about that confusion

I was "Dutching" probably a couple of hours before the jump, so a potential max price limit would help.
Certainly needs a bit more attention.

Too much on this weekend to have much of a go myself, but when I can I'll try out on slightly adjusted rules :

Handicap Races but not maidens.
9-13 starters after scratchings.
First 5 in the prepost market taken from R & S.
First 5 in API (Ave Prizemoney Index).
If 3 or less qualifiers in a race, back them for a win or Dutch them.

Thanks again Bhagwan for pointing us in the right direction

Regards......Mancunian