We make leaders for the Grace frames where I work. The best fabric is a woven polyester, that won't shrink when you wash it. The heavier cotton fabrics shrink terribly. We get whatever is best from a fabric clearance wholesaler. So we've tried several different fabrics. Even the HandiQuilter leaders are made with that thick cotton, and say right on them that they are NOT washable. If you do get a heavy cotton, pre-wash it and dry it in the dryer to get it to shrink before you cut and sew.