I cut it out, there's a start, and pinned up the en fourreau back pleating, using pgs 49 - 50 in Costume in Detail: Women's Dress 1730-1930 as a guide.
|Image from Costume in Detail, page 49|
|Image from Costume in Detail, page 50|
I also tried the front and side back pieces combined, with no extra side seam. With this method, you smooth the piece around to the back, turn under the raw edge, and top stitch it along the curved side back seam with a back stitch (by hand, of course). I'm nervous about losing the control in fitting a side seam gives, but I want to at least try to try to historical methods, and the Williamsburg polonaise seen in Costume Close Up: Clothing Construction and Pattern, 1750-1790 uses this method.
|Lots of pins, to see how things will lay and look. Next is to sew all this stuff for real-real.|
|Front looks nice and smooth, just pinned into position. The strap will be handy in adjusting to length of waist, too.|