Out of interest I looked at yesterday's S.P. results.

The two rules I used were:

1) Fields that had 9 to 12 runners.
2) Bet all S.P. prices that were $29.90 and less.

There were 25 races, the winner was struck in all 25.

The outlay ($1.00) was $168 and the S.P. return was $197. I applied Betfair's commission to the winner's price and not the race's profit (if any), so the real result would have been slightly better.

I hope to look at the results of other days, and if worthwhile I'll report back here.