Glenno.

1. Pre post markets as the basis for your assessment of a "favourite" is dangerous. By my observation only about half the newspaper faves actually start favourite.
2. The SP fave is not know until after the race when the SP is actually declared. Know any bookies who let you on after the race?
3. TAB prices fluctuate wildly. The 4th favourite 30 seconds before the jump can start favourite in reality.

I don't see how any accuracy can be attained by any of the above methods.