Since my last substantive post:

Pinned collars in place along their finished edge, to establish final position.



This left me with misaligned raw edges, so I needed to establish a sewing line along the neck edge. Based on available real estate, I measured 2.5 inches from finished edge of collar and pinned along that line.



I will fiddle with that line later, as you'll see, but it gives me a good starting point.



Then I basted along the line of pins, both to hold the collar in place during sewing and to give myself a visual guide for machine stitching.