Maybe a rag quilt with nothing on the back. Just cut the squares and sew them together with no backing. The s-shirts are warm and after so many will be heavy. Use a stitch I saw on Sewing With Nancy, she called a wobble stitch, a very narrow zig-zag stitch, just enough to zig-zag and about 2.5 length. This will make a stretch stitch. Good luck.