Ratings staking help

I am after some advice on the best way to stake ratings. I am looking at betting the top three horses. I have played round with a few different ways so far, and am just trying to find the most efficient way. So far I have gone through yesterdays racing and bet with three different methods.

method 1:
1 unit on each horse

method 2:
3 units on shortest, 2 on second shortest, and 1 on longest price horse

mthod 3:
3 units on horses under $5, 2 on the $5-$10, and one on anything over $10

These are the raw results from yesterdays results

Method 1:
8% LOT

Method 2:
10% LOT

Method 3:
12% LOT

In a few of those raw results, even though one of the horses won, the result was a negative due to the horse not paying with a high enough divi to break even. Particualry in races with a horse odds on, I am unsure the best way to play those races as of yet.
Anybody got some other ideas on the best way to stake the top three? Am not so keen on dutching them outright, as it seems you miss the value in the $20 winner that gets up every so often.

And also thoughts on what to do when one of my top 3 are short in the market?
Theres three ideas I have in regrds to this situation:
1: Back solely the short priced horse
2: Back my other two in the hope to snag some good odds if the shortie fall over
3: Skip the race.

So any thoughts on the above would be great.

P.S So far overall the rating are shwoing a tiny profit using method one that I outlined, however this is over a limited sample so far, so am perhaps doubtful wethre this will continue, but showing enough promise to spend some time trying to stake efficeintly.