Okay, so let's see this thing close up.
On my weapon system, this is how it is set up. The base is not intrusive on the rail. It is very slim and compliments the weapon nicely. It's not bulky like other light mounting options are.
The components come to you like this. They are actually in separate baggies. The hardware and allen wrench are in one bag. The other components are in the other. This thing is pretty sturdy. I think that if you were to break this in the field, you'll probably be breaking your weapon too. Dare I say I'd break my rail before this mount?
Now don't let all these small pieces intimidate you. It's pretty easy to mount. The instructions included are very detailed, albeit a bit non-intuitive. I'm a generator technician by trade and I still needed to read the instructions twice. That's okay because once you get started, it pretty much assembles itself. Mine came with a 1" ring to accommodate my Elzetta ZFL-M60.
After mocking the mount up, I put blue loctite on the threads to keep them from coming loose. I'm using blue loctite for now. If heat becomes an issue, I will switch to red, but for now I want the ability to move it around if I need to, but have it rigid enough to stay put while testing.
The mount is offset at a 45 degree angle, which tucks the light up close, but not too close. The drop wing mount would have been a little tighter, but would present interference issues in my application, which is why I opted for the Thorntail to begin with.
As of this writing, this is the only picture of a Thorntail mount on a Ruger SR-556. Just check out the clearance between the set screw on the light ring and the picatinny milled section of the gas regulator housing. Yeah, there isn't much there. It fits, however, and that's all that matters. All parts are made of aluminum, and the flashlight/mount combo do not touch the regulator housing in any way, so there is no direct heat transfer point to the light or the mount.
On the back side, you can see there is plenty of room to get my thumb between the back of the light and the sight detent so it can be put down without a hassle. Of course, when the light needs to be deployed, the detent does not have to be depressed, so it's a non-issue in emergency deployment. Still, the light is far enough away to help avoid a negligent light discharge when the sight is deployed.
As you can see, I can run my grip out toward the end of the rail. My thumb sits just above the mount base, right where it needs to be in order to activate the flashlight without changing my overall grip. I dare not run my hand any further forward than this due to the heat generated by the gas regulator housing. Even then, I will be wearing gloves unless I absolutely cannot stand it.
For more information on the Thorntail Adaptive Light Mount, or the Drop Wing, check out this video.