Are you sewing the whole length of the fabric, 40" or did you cut them in half and sew 20". That is one important thing that Mary Sue Collins talks about in sewing small strips of fabric. Also, if there is still a problem at 20" decrease the length one more time. Less chance of the above comments to occur. I have done several of these strips, I love bargellos, and this can happen with larger pieces as well because something just was not cut correct to begin with. Another thought might be the top pressure coming down on the presser foot to the fabric, you may want to either increase the pressure or decrease. Did you starch your fabric before cutting? This would eliminate any stretching that might be happening. If you ahve cut them, then go ahead and give them a starching and ONLY PRESS!!!!! no ironing. That should allow some stability in your fabric and will match up with that batik you are working with. let us know how it goes again.