I believe the idea of framing a market is to work out you average strike rate, say 65% with you top 4 selections ,plus the 15% that the TAB takes out of the price the put up .
This totals 80% this could be the correct market % to work around.

We as punters are always competing against that 15% take out , thats why so many punters complain that they only manage to break even with a number of good handicapping techniques.

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Cheers.