The fit is not bad. Not perfect. But not bad.
There is some wrinkling, but since it looks pretty even and is all horizontal I think it’s from using thin muslin and not having the boning secured at the ends so the fabric is sliding. I think. It could be that the extra half inch I added between the waist and the underbust to lengthen the torso is too much. Here’s an out of focus side view.
And an even more out of focus back view.
I am so glad I added to the top edge of the original pattern. I'd be a goner if I hadn't. Still, I felt I needed more coverage. After I pinned the excess fabric at the seams, I pinned muslin to the mock-up and drew in a new top edge.
I also marked a new bottom edge, taking about an inch off. I'll make all the changes to the pattern and then it's time to cut the real fabric. Yea.