I've totally finished this wall hanging and delivered it back to its original owner. She is very happy with it! And I'm so glad.
Here are a few more process picts and the final product...
A finished square (more or less, its a bit off square) but it still needs to be trimmed. There was a buckle/bubble in the middle of the star that I was really worried about. I took in the seams a bit - lost my points in the centre, but I felt more encouraged that it would lie flat. Incidentally, when I basted it before quilting, it stuck down with the spray adhesive and there was no more buckling.
Auditioning borders and binding:
What I did for the binding was take some of the leftover ribbon and sew it on the front, with a 1/4" seam allowance. I did opposite sides of the wall hanging first, and just trimmed those tails square. I wrapped the binding around and stitched in the ditch from the front to catch the binding on the back - like you'd do for regular sewn on binding, except it wasn't folded. On the remaining opposite sides, I wrapped the ribbon around the bound side and secured it
Then when I flipped it
Then I trimmed a little and folded it like wrapping a corner on a present. When it was stitched down, all the edges were neatly enclosed and I didn't have to wrestle with trying to fold the binding in the corners.
I added a sleeve and 2 triangles in the bottom corners - in case it needed to be held in the bottom too.
Here's the finished product. It's roughly 36" square.
And the back side. It's very lightly quilted (around the outside of the star, the spines, and in the middle; then both borders).
I am happy with how it turned out and the struggles while making it were worth it. My friend is very pleased and will certainly enjoy it. I included some fabric so she can make a label and a sheet of care instructions for it as well. I would make one of these again - now that I've done one I know what I'd charge and what I can and can't do.