Hi Shoto,
The pre-post market they have is actually sydicated to a number of newspaper groups around Australia so it is reasonable to assume it is very close to papers who maybe use another source for their prices .

The newspapers tend to vary the source they get their pre-posts from on a daily to weekly basis.

As we all know, the pre-post market should be used as a rough guide to its possible final price because most pre-post markets are set at around the 150% mark & the TAB is set at 116.5%

I find the pre-post market excellent for deleting horse in the 2.9/1 range & less because they are poor value long term to show a profit.
You could maybe also delete horses in the 16/1 range & higher because of the low strike rate.

I have found the best value to strike rate is in the 3/1 to 9/1 range.
I have found by doing this to most systems, it nearly always improoves its POT or it reduces its losses on a run of outs.

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Cheers.