Heres one way to increase your SR using your ratings & a spread sheet.

.Whatever your ratings tell you only , they become a selection if they are also in the first 3 in the pre-post market as shown in newspapers or on-line markets such as Racingandsports.

.Delete any that are $3.10 & less in the pre-post market as shown in any newspaper or online pre-post market.
I have found this to work well so as to squeeze a profit from something which would normally break even.

.Fields of 15 runners & less.
Any more & the stats usually fall away

I feel your SR will be approx 25% , the next stage is to only bet the selections using say IAS or Sporting bet, best of 2 totes if one wishes to place all bets at once, because the TABs are natoriously bad value when it comes to the first 3 Favs
It makes a dramatic difference to the POT if you do this.

Example , I noticed one of the plans I was using made 9% POT
Using IAS Superbet & the same selections it went to 26% POT
I placed half my bet with both at the same time over 500 bets over 3 months betting 7 days a week.

One will find that the TAB generally pays more on selections that are approx $6.00+ range & these are the ones that dont win as often.

Using a Data base could be even better, but will require a lot more work keeping it updated manually.
One may like to consider one of the commercial Data systems like Price Predictor or GTX for this alternative, where data can be updated at a click of a button.
GTX has a pre-post market as part of its package.
All this of course, comes at a price, which one has to justify.

I wish you a speedy recovery from a very painful experiece.

Cheers.

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Cheers.