You can run a test by applying a finishing tape, let dry overnight to be sure, then run the iron across the tape at 250 with some pressure. Let cool for 2 min then turn the iron up to 350 and run it over the same tape to see if the edge shrinks back. If the tape pulls on you then check to make sure you have good glue penetration of the fabric. There should be hardly any air bubbles in the glue on the finishing tape. Try a test with medium and light weight tapes. I don't know if one shrinks less than the other. I think the light would resist shrinking more
Jason