I would like to comment as to why certain rules seem to eliminate the losers from the winners.
Am just thinking sometimes there is no logic in why a certain rule should improve the profit ratio.
Could it be a coincidence,or perhaps a bias in designers mind due to the fact that the designer already knows the past results.

Seems the major criteria in your system is that the horse be in the top 3 saddlecloth numbers.
All other rules are only there to sort out which races are inferior.

Rule 1. 5 to 8 starters.
Certainly cuts down on the number of opportunities.Can't quite see how it improves the top 3 numbers' chances.
Less interference in running perhaps.

Rule 2.Up to 1200 metres.
Still not sure how this rule works.Something to do with speed rather than stamina.

Rule 3.Country tracks only.
Could this perhaps be related to prizemoney awarded.How badly do the lower weighted jockeys really want to win.

Rule 4.No maidens or 2yo's
The top weighted horses in these events are quite often there because their name begins with the letter "a".

Please do not get the impression that I am trying to degrade you in any way.
I am well known for designing a system that came up with 11 losers in a row,many at short priced favourites.