I have had success on several of my boats using fishing line to tie the sails to the mast. After tying a knot just go ahead and drop some super glue on the knot so it won't come out. I have also used strapping tape on the leading edge of the sail to keep it from stretching. After adding the tape on the edge come back and cut small holes with a small nail head, then add the fishing line. For fishing line try Triline for bending on the mast and for sheeting lines.

Rick