I,ll throw my 2 bobs worth in.
I,ve come to the conclusion that betting 1 horse a race is for me a recipe for disaster so I multibet a number of horses to attempt a profit whichever one wins.
To do this I use ANY reasonable set of ratings be they R+S - Unitab - Wizard -Giddy Up etc
A cutoff price position I am unsure of but at present $20.
I do like horses up in the weights - 55 KG + (represents 36.5 % of races BUT win 50.6 %) A huge advantage.

Thats my approach.

Re Mechanical systems most I,ve found nearly always lead back to the Fav.
Whether handicapping the eyes out of the fav would be the Holy Grail I dont know but I,ve found that the occassional High priced horse gives me a better all round yearly figure.

Cheers
darky