I mentioned the heat issue on USN when someone brought it up...I don't use my Fenix lights in the brighter modes for long use, only intermittent use. Plus, if you are concerned with that you can pull them off (the head part) and slide it back on later. I've had a few lights wrapped like this for a while with no problems. I wrapped some tight O-rings around the head on my P2D both to keep it in place and as a sort of grip ring while using it in a cigar-type-grip. I'll try and get pics up of it later.
And just like Kydex, you can give it a seconds blast with a heat gun and tighten it up if you so choose...I just haven't had any problems with that sort of thing.