any market watchers out there will note this happening on a regular basis, i tried to build something around it a while back & failed dismally(:

party, i had some fun on betfair doing a similar thing, usually with only 1 or 2 nags in a race, win if they win, win if they lose, wonderful feeling once its all locked in, but again failed to make it pay longterm as too often they shortened when i needed em to lengthen or vice versa

so worked out eventually i much prefer to see my sole selection in the race power home to WIN, i still lay the odd very short nag i suspect cant win, but it just never provides the same level of satisfaction/moola