Backfitting i will say properly wont work at all , but sorting things like >10% win and 30% place and 2 wins or more, to try and narrow done the horses and the fields to find the better horses and races may be of help the bookies are so good at there job there cant be that many areas of profit left. It may be best used to find the areas that are really bad % loss wise over the long term and dont go there to start with and even that would be hard just ask the layers. It needs to have reason for me so i look for the better horses in the better races metro and try to find the horse or horses that are in or seem to be in with a real chance - first 4 in my ratings while i may win outside there it doesnt make that much differnce to my betting as it doesnt rely on the longshot.