All I have to say is that this TSO stuff is a slippery slope. Where does it stop? I mean, I'm allowed to take off my headsets above FL180. What if I then donned my unapproved Bose headset and the cockpit speakers went belly up, what then? What about my contact lenses? Are they TSO'd? God forbid my unapproved writing utensil (ballpoint pen) were to quit.