If you want a gauranteed return for one of your 4 picks winning this is what I would suggest.

First thing is to make sure there is sufficient percentage within your 4 picks to justify having a bet.

For example if the odds on your picks are 3.00, 5.00, 7.00 and 11.00 and you rate everything else as no chance then the percentage in these 4 is 1/3 + 1/5 + 1/7 + 1/11 = 76.3% This is probably enough to justify having a bet. It depends on how sure you are that no other runners can win. If the percentage is close to 100% or worse still, over 100% then keep your money in your pocket.

It pays to find fixed odds if you can get the value, as tote odds may shorten by the time they jump and you will lose the value. Try looking at EDITED for a range of bookies prices betting fixed odds.

Your staking plan should ideally be based on the difference between your judgement and the bookies judgement to ensure you get maximum value.

However to ensure you get a return if one of your 4 picks wins, just adjust your stake to ensure each of the 4 picks will give a similar return.

In the above example, wagers of $33, $20, $14, and $9 will all return approx $100 for a total outlay of $76, so you win about $24 if one of your 4 picks wins.

Be careful, because you are outlaying $76 just to win $24 (3:1on) about no outsiders upsetting your picks. and I was always taught "odds on - look on"