Some one else on another thread mentioned exactly the same thing in relation to running his commercial systems ONLY over races like GP /LISTED with much better results.
In the very short test I have done I would have to agree.

Another idea from a TOP rating man ( using the WIZARD ratings ) was to add the top 5 weight ratings and divide by 5 .Good betting races were those with figures of 90 or less.
Just a thought .
Cheers.
darky.