I've looked at this for a while and it seems to go quite well. Each horse is backed with the field so there's a possibility of getting the quinella once or twice (or, of course, not at all).

TRENTHAM
RACE 6 (Thorndon Mile)
5 6 7 11 12 17 (all with field - cost for $1 = $96)

RACE 8 (Cup)
3 5 11 14 16 18 (all with field - cost for $1 = $102)

Amazing that with two groups providing television coverage of racing that one can't broadcast what is by far the best meeting in Australasia today.

UPDATE
Outlay = $198
Return = $55.6

I'll keep this updated for a year or so but there will be few bets. The research I have done on it favours high quality races and big fields. It was not typical that both favourites should win (or more importantly for this post run 1 or 2) such races but both these two are very classy and in form. Although its of little import as I don't believe in retrospectivity on the tip this one snared the $398 Vonusti - Tootsie quinella on the big NZ sprint last Saturday. (Trust me!)