If you are going to establish the cable on the outside of the leg before you do any decreasing then I suspect that you will be able to see how the different parts of the knitting match up - shuffle the stitches on the needles to find the centre back.

You might have to use five needles so you can see where the centres should be, or knit the cable side on a circular needle, but the knitting itself should show you where the centre back is.

Anne the Pleater :ootd: