I've been playing around with the toile overnight. Here are some pictures of the final dress pieces pinned on me - note that there are seam allowances on this and that it will look a lot different with boning, lining and interlining. The back neckline is definitely too high and will need to be lowered, the straps are narrow but have wide seam allowance on them right now. The last picture shows that it will have a narrow v-opening once boned properly.
I had this fabric in my stash, and am using the "wrong" side as it matches the portrait better. I would have preferred a more flowing pattern but need to work my way through the stash this year.