Being a longarm quilter I have a few customers who bring sheets for the backing of their quilts. I , nor my machine, have any problem with quilting with the sheets. My job is to quilt, not to criticize. I do find that if an older sheet is used that has been washed a lot, the back stitches look a lot better than if a newer sheet is used. I find even a newer sheet that has been washed will not let the machine stitches "sink" in, they tend to lay on top even with a lot of adjusting of the machine's tension. In my oppinion, it is the tension concern that mashine quilters have, which hand quilters do not need to face. Just my two cents worth.