I made up just the top portion of the Vionnet dress to see how I'm going scale wise. It's cut on the correct (bias, naturally) grain, of lining. And when I tried to slip it onto my dummy it was immediately obvious that it wasn't going to fit. After ripping out the "side" seams I slipped it on and had a look.
You can just make out my stitching lines in white (I marked those with dressmakers carbon before I took the paper pattern pieces off). I didn't pin it terribly evenly so one side gapes more than the other.
It's close enough that I think my scaling is pretty close - it's just a tiny dress! It's also meant to be made from very drapey satin, which would make it looser than my lining.
So, my next problem is how and how much to scale up? My first thought is that with complex and unconventional seaming it would be easier to just enlarge the whole thing by using a larger scale than by any type of grading technique. The problem with that is that it'll make the bodice longer as well as wider, which obviously wouldn't work. So I'm going to do some measuring to see how much extra width I need and see if I can add that in without ruining the lines of the dress. I can sneak a bit in at CF and CB, the rest is going to take some careful thought. The skirt is so full that I feel I can ignore it at this point. It's also so simple that it can be easily adjusted to match anything I do to the bodice without compromising the cut. And Sherry, yes it is slashed at the CB to match the point of the bodice CB. Can't wait to see how that looks!