Sewing On Neck Reinforcment
There are two options on how to do this.
The first is to wrap the strip around the neck, tucking the unfolded end into folded and sew down the ends, with a few additional stitches into the neck to secure it.
The second is to whip stitch the two edges all the way around.
These pictures are the first time I've done this, previously I either left it as it was (having used strong thread for the running stitch), or slip stitched around the neck attaching the head and shoulders to each other about 1/2 cm (1/4") from the line of running stitch.
Re-enforcing the neck is a good idea, as the running stitch could snap and you'd find yourself with a linebacker in a dress.