Hi all, I hate to sound like a broken record but so far nobody has disputed my post that boxing quins and trifectas is betting against yourself. I acknowledge that it is nice for the nerves to get regular collects but when most people use computers to rate races why don't you just bet on more races in a day rather than box? I don't look to include long-shots in my selections as there is generally more value (i.e overlays) when short-priced runners get up. It seems the sort of people who are attracted to exotic bets are going for the big collects/thrills rather than constant profits. I bet they ride motorcycles too!
As for filter-type systems I think that once it gets as complex as above you're better off just scrolling throught the form and rating each runner out of ten. The human brain is an amazing thing and will incorporate all the various factors and also dismiss anomalies which mechanical filters overlook. Happy punting!

I was reading somewhere that Quinellas in races with exactly 9 runners offered the best chance for profiting.

Exactly 9? :???:

I think it was a reference to Malcom Knowles Quinella booklet but it wasn't exactly 9 runners. The percentage of quins that were an overlay decreased as field size increased but it happens in a gradual way ( as you'd expect ) and there was no clear cut-off point.
I did a science course at uni and had 4 years of Stats as a result. One of the fundamental questions you must ask when evaluating the outcome of an experiment is "is there a SIGNIFICANT difference in the outcomes". There are protocols and calculations which can answer this question but these are mostly ignored by many punters who can be misled by a shear weight of data such as "10years of races and 33000 races"
One of the things I love about punting is that at the end of the day all theory is tested in very rigorous manner i.e your bank is up or down and you can't argue that outcome!