When I used to quilt on my domestic, I found that my spacing bar would sometimes move in the process of manipulating the quilt around so I use masking/painters tape to do any spaced quilting greater than 1/4". I would quilt right next to the tape. You can use a strip several times before it quits sticking. I would not quilt anything with lines spaced greater than 2" unless I was going to put some kind of fill in the area. In those cases I would line up two strips of masking tape side by side and remove the one that wasn't going to have quilting next to it. It is difficult to find painters tape wider than 2". In my experience anything with larger spacing just doesn't look that nice after washing.