When you use a longarm quilter, it’s easier for the quilter if you use a wide backing. If you are piecing your quilt back, then have your seams parallel to each other and ask the quilter how they would load it so you know which direction to have the seams run. If the quilt is loaded with seams parallel to the bars, you will have a constant and equal tension on the seams. If they are perpendicular, it’s not an even pull from the side clamps and sometimes the seam has difficult-to-manage “bat wings” from how it’s sewn together. You want to make it as easy on the longarmer as possible. Less problems = better result.