Results for Sat:

Return 67.00
Outlay 103.00
Profit -$36.00
POT -35%

PURE SELECTIONS LOST 86%
NON PURE GAINED 18%

So no real indication that I am on the right track yet with this system.

I have identified some filters to restrict the races selected where the 1st or 2nd favourite has good odds and actually does win. But further investigation is required.