My daughter fleeces most of the backs to her quilts and cotton on the front. When I use fleece I use the walking foot, it really helps keep from having pleats and bunched seams. I'm not sure about doing the HST using both fabrics but maybe do the cotton with HST and sqaures or a pieced backing for the fleece or even use the fleece and cotton to make rag quilts. The fleece won't ravel but it will curl so it makes really nice rag quilts