Into the home stretch!
First, I had to adjust the back, where I had added an inch extra width "just in case". Not only did I not need that inch, I had to take the back in by another half inch on both sides.
I sewed a new line of basting where the zipper will go and basted the raw edges together and then cut off an inch and a half on both ends of the back. Unfortunately, this made the tops of the two back pieces no longer line up, because they are not mirror images of each other.
I thought about taking the side that was higher all apart, which would include undoing the understitching and everything. Then I thought I would never get it lined up as well as if I just folded it over so that's what I did and sewed it down with tiny stitches. After I press it carefully, it should be invisible on the outside.
Now you can see how the top edges will line up properly once the zipper is in.
Next I hand basted the upper and lower edges of the bubble skirt, so that I could make the gathers evenly. That went surprisingly quickly.
I pinned the soon-to-be gathered skirt to the skirt lining.
And the gathers were remarkably easy to make too. I may have to consider hand basting all my gathers from now on. The thread is much looser than if it was machine basted and so it is easier to pull.
Here, I've sewn the skirt to the lining around the bottom and given that seam a bit of a press in anticipation of understitching the lining.
Here's the bubble skirt, sewed top and bottom to the shorter, narrower lining. I'm ready to attach the skirt to the midriff and the last step will be putting in the zipper!