Barny with your 12 years of data are you able to run me a little test of a mechnical system I used to use.

I looked at Metro racing in Melbourne, Sydney and Brisbane only
Must be API = 1
Age is a 5 or 6 year
Win % must be over 26% and the place below 50% (i'll give my reasons later if this has held up over the test of time)
Weight = 55kg to 59kg and last margin is less than 5 lengths.

Summary below:

Vortech Metro Rules
Venue: MSB
Age of Horse: 5 - 6
Horse Win %: 27 - 100
Horse Place %: 0 - 49
Weight to Carry: 55.0 - 59.0
Last Start Margin: 0.0 - 5.0
Av Prizemoney Rank: 1 - 1