I have BERNINA machines. I like to use a 1/4" foot. However, I know that I need to hold my fabric pieces against the right edge of the feed dog mechanism. I also pin to keep my pieces together. Like Jan mentioned above I use an awl to hold the last inch or so of fabrics up against my guideline which I make using painter's tape. I am going to try Jan's rubber band method. I should say that I just finished piecing a quilt that is 100 X 100 inches and was off by 1/4" on the total width. I feel I can live with that! I think each person needs to find their 1/4" (PPM). Test each time you make a quilt because fabric and thread size can make a difference. Results are happier when you plan and adjust rather than just guessing.