When I was having big problems with the tension on my Janome 4800 while doing FMQ, Janome actually recommended that I use embroidery thread (their brand, of course!). I tried it for a couple of wall hangings, and it did work much better - and like you, I loved the sheen on it. For a wall hanging, it's probably strong enough. I now think that the machine was a lemon, because since I gave up and bought myself a new one, I've suddenly had no more problems with FMQ!