SID is one of my preferred machine quilting stitch - along side cross hatching. I really never thought about quilting on the seam, beside the seam, etc. However, having watched Georgia Bonesteel on cable, she uses a narrow zig-zag stitch when she does SID. So, if it's good enough for her, it's good enough for the rest of us, as she's a nationally known quilter, although she usually hand quilts everything. Take your pick with the options and remember - THERE ARE NO QUILT POLICE, only other quilters who will oooh and aaah over your beautiful quilt.