I believe that JTECs stance is their muffler is very light, "very little mass", therefore a strap is not required. Interestingly enough I just purchased a new Slimeline wrap around style muffler for a DA50 and they have also eliminated the strap. I had a JTEC muffler basically disintegrate into two pieces on a DA50. I believe the contributing cause was long standoffs that had compressed into the plywood firewall at the mounting point. This created a lot of engine oscillation. Maybe a muffler strap would have saved the muffler, hard to say. I decided that a better solution is to mount the standoffs to an aluminmum plate first and then mount the plate to the firewall. Much more rigid setup and more surface area when mounting to the firewall. I also switched to an older Slimline muffler, one with a strap, because I felt the Slimline muffler was a better quality muffler. Just my opinion.

I totally agree with kmeyers, pe reivers and arobatx, use a muffler strap. Be sure the muffler strap is connected to the engine, not the airframe.