Great article! It's really helpful to see where you had trouble, and what you wound up doing to sort it out.
I have a pair of modem men's trousers whose (separate) waistband has a curtain. I don't have them on me to look at (ha), but if I recall correctly it is just cut on to the waistband lining. The whole inner structure is much longer and the two layers are connected only by stitching in the ditch at the waist seam. Then the curtain section hangs down over the raw edges. I can't remember how the edge of the curtain is finished. It is either turned all the way back up in to the waistband structure or it is bound along the bottom edge.