As mentioned several times, sew your Thangles using a smaller stitch length. Then, after you have cut the pieces apart, lay the triangle on a hard surface and fold the paper along the stitch line, creasing with your thumb. When you tear the paper from the outside edge between the stitching and the point, not at one of the stitched corners, and tear the paper down to the stitching. Then remove the two large pieces, then the two selvage pieces.