Further on this I can see that a single straight tri bet per race using Don Scott's Ratings is too much effort for potential reward.
Does anyone have placing percentages for each of the second,third fourth etc favorites? Could you please post them? thanks in advance.

I can see that by ditching the races where fav is <$2.5 and less than 10 runners will provide better payouts. The big payouts are where 2 or 3 longshots got up. The reasonable payouts are where the fav 4-8 have got up. Favs that are more than the tenth favorite are few and far between <2% winners.
I am thinking that by using fav4-8 for the first leg and top 4 for the second and third leg and see what that looks like.
Regards Beton