Sally Collins, author of a book on precision machine piecing, recommends you have the entire narrow black line (not the fat yellow line around it) on the fabric, without showing any fabric beyond the line. The thickness of that line makes up for the thickness of the thread and what is lost when you turn the seam allowance to one side, so in cutting that way, there is no need to sew a scant quarter inch. She has lots of other tips for accuracy in quilting. I highly recommend her book and workshop.