I remember that Mark posted a thread some years ago re firmers on opening prices.
I am thinking off the cuff here and out loud. This is to encourage some positive debate here. If the prepost market in one form or another produces an 80% plus strike rate in the top 5 (it seems that it does not matter which source so long as it is consistent) and the tote produces a similar result in the top 5 favorites, (not necessarily the same horses) and the winner is usually (noticibly better than 50%) then in a rudimentry form we could do the following. Take the top 5 prepost and back them at the best prices that we can get. Then lay those same 5 (or the top fav on tote) at the starting price.
Where it counts the price should be shorter. Swings and roundabouts over time it should be in the positive.