I have a long arm & haven't experienced the problem of bunching, but it's probably because I have only done laps on it. I prefer one piece backs, just because they are simplest, but....What I do like, is to use 3 or 4 of the fabrics from the front of the quilt & make horizontal strips with the fabric for the backing. This gives you a reversible quilt with little effort. It truly is easier to keep the horizontal seams straight as opposed to the vertical ones.