Because I really can't leave well enough alone, here's the pic I took after I pressed the CB seam and checked that the dress was hanging straight! It's still not perfect, but I declare it Good Enough. The slight rippling you can see in the zip seems to be caused by the gaps between the sections on my dummy. As far as I can tell when I try it on they aren't there.
Now I can move on ;-)
Butterick 5600: the business shirt turned dress(y)
31 minutes ago