I just like betting to my asessed price.

In your 6/4 example $2.50 = $40 then anything at this price or better would still have $40 placed on it.
If the bookie offered me 10/1 I would win $400.
A very simple,easy, and good way to keep track of your staking in my opinion.

Thats just what I would do.Everyone would have a different opinion.

Cheers.
darky