My SID foot stitches just a stitch width to the right of the ditch, so I use a matching or invisible thread. However, in doing my last SID project (king sized quilt), I had some issues with the metal bar getting hung up where points met. Also, since it only allowed me to sew to the right of the ditch, I had problems with quilt bulk; I changed to a regular foot which allowed me to sew either right or left side of the "melons" that I was sewing around. My accuracy was as good as, if not better than when I used the SID foot.