Made my corset mock-up today. It was a little loose through the bust and hips, but as cotton duck has some bias stretch whereas the coutil I'm going to use on the finished product does not, I'm going to stick with the sizing. The waist cinched in nicely, and I was quite happy with the shape. It was, however, too long on the bottom, so I marked with a pencil the almost 2" that need to be removed in some places, while also realizing that it's a bit too short on top. I added half an inch in front, curving it around to a full inch in the very back. It was comfortable, and I think it will turn out very nicely.
The corset was tested using the new lacing strips I made, following this tutorial by Bridges on the Body.