If I understand correctly, the wide red stripe should be in the center of each pleat, with the white and black stripes on each side of the center. I haven't run your numbers, but let's suppose that your 19/32 at the waist and 11/16 at the hips are correct. I'm not sure why you're measuring only half that width when you pin a pleat. The whole pleat should be 11/16 at the hip and 19/32 at the waist, and the center of the red stripe should be centered in the pleat both at the waist and the bottom of the fell (at the hip).

You should start by folding the first pleat at the full pleat width at the waist and the hip, with the red stripe centered all along the pleat, and then stitch the edge of the apron to both layers of the pleat that you have folded. And yes, once you have sewn that, there is no way that change the size of that pleat, which is why it's important to get it right in the first place. After stitching the first one, you'll fold the next pleat at the full width at both hip and waist, with the red stripe centered, and then stitch the edge of the first pleat to both thicknesses of the pleat that you have folded.

Or maybe I don't understand your question??