Here is a simple system for backing the opening favourite (using Betchoice opening prices).

Only consider the Opening Favourite (no equal Favourites).
Aim to collect a certain amount, say $20
Use the opening price to determine your bet, say opens at $3.00
Bet will be 20/3 = $7 (always round up)
If bet loses new Aim will be 20 + 7 = $27
Follow the same process for next race if no winner proceed for a third race which ends the series irrespective if a winner is found or not. Start again next week aiming for $20

If bet wins end series and start again next week aiming for $20.

A winning bet always ends the series irrespective if you do not cover your outlay.

If the next race has equal favourites, ignore race and proceed to the following race to continue process.

Example

1/1/2011 Randwick

Wakanda opening price $2.60 ..aim $20 ..bet $8...loss
Glissade opening price $2.40 ..aim $28 ..bet $12..win $2.50..collect $30.00

Outlay $20
Collect $30
profit $10

Results of Saturday meetings in Melbourne and Sydney since 1/1/2011 are:-

Melbourne (aiming for $20)

149 bets
55 wins
36.9 % S/R
Bank $216.55
13.5% POT

Sydney (aiming for $20)

137 bets
53 wins
38.6 % S/R
Bank $144.05
9.1% POT

I have not looked at other Metropolitan races nor have I looked at Country or Provincial races.