On the long arm I will use 2 layers (80/20 on bottom, wool on top or a med. poly on top) to get more definition with my quilting. Especially like it when quilting an applique or embroidered quilt, gives that faux trapunto. On a very large quilt it will make it pretty heavy. I did use 2 layers of med poly on a wall hanging that I did for a show and it worked very well too--wanted poly as it doesn't hold onto creases as much as wool or cotton.