I've got two Tower .75s with several flights on them, and I haven't had a problem with either muffler coming loose. I always put Tamiya threadlock on the bolt/nut and tighten it up good, never had it come loose or rotate on me. The Tamiya threadlock is gel, unlike the runny Loctite threadlock. I put it on all my muffler bolt/nuts, and I have not had one come loose since.

Yeah, the Tower .75s are a little loud, but they sound great to me, and put out plenty of power. Excellent value for the money.