Had a play with GEELONG Race 4.
Its a 347 metre race and you would be kidding yourself if you could do better than pick more than just the winner.

3 POLLY'S CHOICE 0.0 $4.8
7 CAPTAIN MILO 0.2 $5.3
6 COULTA SALLY 0.7 $6.6
2 RIVERDALE LESTER 1.1 $8
1 REGAL CADET 1.4 $9.3
8 SO SAUCY 1.5 $10
5 DYNA ROSE 2.0 $12
10 ANGEL TY'S 3.6 $25

These margins I came up with will cetainly not be even close to the actual race results.
They are more an interpretaion of how it is easily possible for any dog to win this race and is mainly a race of Luck.
And the luckiest dog will be the one that leads.
Stay out if you can Gamblerholics.