There is, of course, also the issue of... underwear. With the dress I wrote about goes a specific underdress, also a reconstruction, and also one that was probably not made of one hundred percent good choices.
When I looked at images of the dresses with the pendant sleeves back when I did the reconstruction, most of them showed a kind of pleated sleeve on the women's underarms. So I went and did a pleated underdress with a pleated sleeve - preparing the pleat lines by drawing a needle tip through the fabric and then pressing the pleats in with a glass slickstone.
It did work quite well, but after washing, the pleats do mostly fall out. That's not such a horrible thing on the body of the underdress, as the pleats are only, if at all, visible at the neck opening, but the sleeves... well.
After fiddling around a bit with re-pleating them, trying out various methods and sequences and even using a (modern) iron, I did come to the conclusion that the easiest and nicest way to get the problem fixed would be sewing in the folds.
There was a bit more fiddling and then the additional insight that it would be much easier to get the folds in properly with less fiddling and more space to work. So I un-did the seam holding the underarm part together, unfolded all the thing, and then set to work sewing in the pleats.
It was still a little fiddly to sew them in, especially towards the top (where, thanks to the still complete seam, the sleeve wanted to curve) but it was much less obnoxious than trying to get everything sorted with the seam in. And in the end, I was successful - the pleats are not completely regular, but I don't really mind. They are in, they are fixed, and I will be able to wear a properly pleated thing on the weekend of the demo...