I took a pattern off of my second to last mockup and then made one more mockup off of that this past weekend. I'm happy with the results and ready to move to the real thing.
Here's the second to last mockup. I drew around the pattern pieces in sharpie directly on the mockup so I could trace them onto paper.
Then I unpicked the seams and laid the pieces out flat.
I then traced the pieces onto tracing paper and later added seam allowances.
Afterwards I used this pattern to make a final mockup, to check for accuracy. I only found one place where I messed up the pattern (one of the gussets was traced off too deep).
I've got a big lacing gap because I found on my last stays that they stretched a lot in the back.