As a handquilter for hire I always start in the middle. I don't handquilt in the ditch on anything instead I echo quilt the seams in the sashing etc. I stitch about a 1/4 inside the seam line. It has always been my theory that the quilting reenforced the stitching that assembled the quilt. When I machine quilt I use a decorative stitch that overlaps on both sides of the seam line. If you stitch inside the seam what will keep it from coming apart at the seam.
As a handquilter I can stitch the borders etc. almost as fast as I can machine quilt with the added bonus of being able to watch TV or even hold a conversation while quilting.
Whatever you do I hope it turns out beautifully.
Mary