There is also a good tutorial here:
http://www.quiltingboard.com/t-89997-1.htm
The problem with a 1/4" foot is that the scant 1/4" may change with the thickness of your thread or fabric. You'd need to take a slightly smaller seam with flannel than with quilting cottons. If you always use the same weight thread and fabric, you can figure out where the sweet spot is, mark it & use it forever!