Thanks everyone for your feedback! A resounding chorus cried out for no underwaist and I will be heeding them.
The pro-underwaist movement liked them (or the idea of them) because the underwaist helps hold skirts in place when you have a rectangular body shape. Since I got 99 problems but an ill-defined waist ain’t one, this doesn’t color my decision-making.
Now I am building up the nerve to also forego the separating zipper in a box pleat at the back of the blouse. Why would you want to make your blouse more difficult to put on? What was going on back in the Sixties??
I am also petting my piles of wool, linen, and poly suit weight fabrics to decide who gets to grow up and be the skirt and jacket of my three-piece ensemble