The answer was to cut a notch. This tiny cut made room where there wasn't any. It had to be done with a sharp X-Acto, one edge at a time, by eye. In hindsight I should've put in a core wrapping, to help shaping, but the notch worked out anyway.
A whole lot of pulling takes place during these steps. In particular the white core will get pulled, and inevitably it gets longer. In hindsight (again) I should've allowed for this lengthening, and hung it a little shorter to start with.
Below, you can see the checkered strands held to the side (the clips), the completed white/green/white, and the blue in mid-spin.
I ran out of one of the checkered strands first, so that determined how long it was! The last part of any mecate is the tassel knot. Here I've started the core of the tassel knot: a 4-part Undercrown, with the white core strand as a center.
My attention went to the popper end. I needed another knot to tighten up the rope and disguise some ends. While full-scale mecates don't have buttons here, I frequently need them for construction purposes! At least it will match.
And this one did.