Here it is blocking with a million pins:
And here it is, finished! It's relaxing just a bit and the centers of the sides are pulling in just slightly, which is neat.
It's 20" from point to point, and I used size 10 cotton crochet thread with a 2.5mm Addi Turbo circular needle.
I can see more of these in my future--this was a great, fun, fast project.