Here are some pics to help me answer ktlovely’s question of how I treated the seams on my 18th century stays. I believe both Hunnisett and Farthingales recommend pressing the seam allowances toward the back, which I managed to do on one seam.
The front seam I pressed open to avoid any unnecessary bulk at the center front (I did double stitch this seam first to make sure it was sturdy though). My side seams are a little wonky because I had to put in that little adjustment panel after I finished the stays. I pressed the seams in the way that made sense for the tabs, as you can see. I then whip-stitched the SAs down by hand. I did the same thing on B’s 1740’s pirate stays by the way, managing to press all those seams toward the back. :>
My apologies for the delay in getting back to you Katie, do forgive me! :>