I use a long arm and generally no problems with pieced backs--just know that it's hard to line up designs on the long arm as it rolls (think of rolling up a magazine and what happens to the pages). My only time it was an issue is when the customer gave me a pieced back that had several different fabrics and one had the straight of grain going a different direction which stretched differently--hard to avoid puckers. With pieced blocks it's never been a problem.