if you do choose to (straight) piece your backing- for long--arm quilting it is recommended that the seam be horizontal-not vertical. this is so the seam can lay flat & even along the take up roller- not build layer upon layer in the center-which happens with vertical seams-causing floppy sides- which on quilts that small are not a huge problem-but you get a better (even) quilt if the seam is horizontal.