Thanks so much to everyone for your embroidery input (below)! Okay, two strands, and mark the pattern shape but don’t cut until after I embroider (since none of the embroidery will be near the edge, I’m going with this plan — I like the idea of having extra fabric to fit in my hoop).
But, of course, I need a fitted pattern first so off I went! The pattern went together easily, except of course I had to sew all those tucks for the mockup as they’d affect the fit. No problem, I listened to most of the commentaries on Titanic (very little costume stuff — there’s a few comments by Deborah Scott on at the cast & crew commentary, and a brief behind-the-scenes where you get to see lots of extras’ costumes in one of the easter eggs [when Jack and Rose are going in to dinner]).
The big problem with mocking this up is that lace insertion and edging make up part of the body of this garment, including all of the armholes. So I had to draw in their widths, cut holes, and loop a ribbon through in order to see the fit. Here it is on my dress form:
All I could tell was that it was too wide, so I took it in a bit at the side seams and tried it on my real body:
The only real issue was some bunching up around the armholes, so I had to redraw a lower, wider armhole.
Then, suffering from Costume ADD as I did, I was feeling too lazy to redo the pattern or mark the pattern on my fashion fabric, so instead I started on a mockup of a new 1910s corset… but more on that soon!