So I have been doing ALL this sewing, but have been too busy to update here! I will parcel it out in bits so as to keep things interesting (rather than dumping it on you all at once).
I spent a Saturday mocking up various boning layouts on my 1780s stays. I found a boning layout that worked very nicely and improved things — but found that even more, the trick turned out to be moving the position of my strap. My first version of my 1780s stays had a VERY wide front, which was great for creating forced posture (ie narrow back, wide front, shoulders held back)… but not so good for ye quadraboob. Moving the strap forward a good 2-3″ tightened things up in the bust and really pushed the girls forward.
So here’s some comparison shots of the various boning layouts and how they worked out: