After posting last night, I stayed up too late again to finish all the weaving in of ends and to try the duplicate stitch for the stripe under the neck. The duplicate stitch didn't turn out bulky at all. In fact, it looks just like the other stripes. There is supposed to be another stripe on the row directly under the neck, but I'm not certain I'll add it because when the sweater is on, the turtleneck obscures that part. I'm sure I'll have to try it though and see what it looks like.