This is in no way, shape, or form going to answer your question, but I'm having a thought about your inquiry. Without knowing exactly what you're making with your silnylon I can't be too specific, but oftentimes you don't HAVE TO heat seal the cut edge of silnylon. The silicone coating on the fabric tends to stop it from fraying while you're working with it, and I'm (dangerously) assuming that you will be sewing this raw edge into some sort of seam which will enclose the edge. Rolled or flat-felled seams seem to work the best for this. They're both relatively sturdy and enclose the raw edge, thereby saving you the heartache of melting the edges. That being said, if you're using a simple stitch that leaves the raw edges exposed, you should probably wait to see what the other members have to say about that snazzy little iron gizmo. I hope this helps. Take care!