I sew my binding to the back, then sew the serpentine stitch to the binding on the front. I do a test first so I get the width exactly right, then I eye up where the foot needs to be on the binding, sew slow, and keep my eye ahead of the foot. Doing this, I have the stitch edge just hitting the edge of the binding on the back, and it looks the same on the front, just to the inside edge of the binding. I create an actual mock up of a quilt edge with the binding sewn on. I do not like taking out stitches so I make sure I have what I want before I do the actual binding. I also lift the quilt edge up every so often and double check the sewing on the bottom-with the needle down. Since every binding doesn't always end up with the same width on each quilt, I need to do these tests first as the width may not always the same for the serpentine stitch I am sewing. Changing the length and width of the serpentine stitch gives different looks.