Take for example the IAS top 4 or any set of ratings. If you can consistently eliminate one or maybe two of the top four, ie able to lay these selections to make a profit. Would you automatically be on a winner by backing the remaining of the selections from top four, as you are eliminating generally a horse at shorter odds, and therefore a decent whack of the market percentage? If its a $5 horse, you are taking around 20% out of the market, so BF in particular you would be backing into a 82% (roughly) market, instead of a 102%.

eg

IAS Top four
1,2,3,4,

You have a lay system which selects horse 3, so you lay 3, and back 1,2 and 4.

Would this work?

Thoughts?

Short answer - Yes

Long answer - it depends on the accuracy of your elimination method. If you could eliminate a short(ish) priced horse every race 100% of them time then you would of course profit. The key in anything like this is about how accurate you are and that can be hard to measure.

Lets assume you get it right 80% of the time and take 100 examples of your 4 horse race...

* 80 times you would be able to make an 82% book...$18 profit per $100 staked = + 1440
* 20 times you would lose the $100 staked = -2000

So in that example you're down $560. And that is with what may be considered a fairly high accuracy level. The hard part is that every race is different - different number of runners, different horses, different odds so you will neve get an exact measurement of your accuracy at any given odds level.

Cheers for the reply. Had a play with the idea yesterday with some success. I only backed those in races where I had one or more of the top 4 IAS as lay selections. Ended the day 5 units ahead, and going back over Monday and Tuesday, there was around 30 units from those two days. Too early I guess to know if theres anything to it, and if I have just hit a lucky period, but will continue to monitor it for a couple of weeks.