This method is a little like one used by Ricky Tims in his videio 'Grand Finale' - it's a video well-worth buying! He uses a slightly finer fabric for the insert, placing a length of embroidery thread in the middle of it to make a very fine piped edge. It is then turned to the right side and stitched in-the -ditch so that no stitching shows. I've tried it and the result is exceptionally good - looks very professional!