Square 7 - a bit of it anyway!

I like this stitch pattern, I'm thinking of making a scarf with it sometime soon, it'll make a change from eyelash yarn scarves, and anyway I've nearly finished knitting up all the cheap acrylic eyelash that I have and I won't be replacing it unless someone orders something specific.

I'm worried about square 8, Barbara Walker makes the point that this stitch is very stretchy and makes it with only 30 stitches cast on, but look how much smaller my first try was when I was working with the other colourway compared to the garter stitch square, I'm trying to decide if it really will stretch that far or if I should add a few stitches. This si the next square if I knit them in order and I'm not sure how to proceed.