I've adapted some suggestions made here on the forum to look at a Lay the Fave method. There are only two filters to select the right race inwhich to lay the fave:

1) Race 4 and onwards.
2) No races from tracks at the major cities.

I've looked at results from the past seven days, and used the NSW TAB fave and their divvies.

There were 149 races for 107 smiles, or 101.65 units. The total liability from the 42 accidents came to 55.40 units. This is about a 80% profit, but even with Betfair's higher prices I think it can be safely assumed the method would have an acceptable profit.

I began to check the results from the first three races, but after a few days stopped because it did not look profitable.

I will from today lay the faves but not them all, because I will not be at my computer for most of the day.