I'm very aware, and while I'd never want to go toe-to-toe with Henry on the heavy engineering questions, I don't think his reservations about it carry much concern. At least, they don't for me. As I've seen it stated, there are ~3 reasons he doesn't recommend it:
1. Waterproofness. He's right on a stock light..but its easily mitigated with a larger o-ring. My HDS lights with clips under the bezel and properly up-sized o-rings have been underwater many times - freshwater, saltwater, pools, rivers, lakes and oceans. As much as 8ish feet down at times. Plus I regularly wash them off in the sink when they get dirty. Zero water intrusion. Maybe if I was a diver it would be different, but then HDS doesn't recommend these lights for diving, so I'm not concerned about that.
2. Focal length. Literally not an issue if you install the clip above the reflector, so its touching the bezel not the body. If you put the clip between the head and the reflector he's absolutely right, the reflector is raised the thickness of the clip and it usually results in an ugly donut-hole beam. Some folks still do this though because it removes the need for the thicker o-ring. But I don't, so the added space is above the reflector, below the glass, which is where the thicker o-ring goes, and the relationship between the reflector and the LED is unchanged.
3. Less threads holding. No argument there, he's objectively correct in this. The bezel now has ~1mm less thread depth holding. But since HDS lights are waaayy over-engineered anyway I think it can spare that mm and still be damn strong. And in my experience it is.
Now Henry could probably come in here with some math and show that the thicker o-ring lessens pressure against the crystal by such-n-such percent, or the strength of the connection between the bezel and the light is now weaker by such-n-such percent, maybe even the distance between the LED and crystal being increased by a mm results in...something negative idk (but not focal length), and he'll almost certainly be completely right, but I still find those issues well within my own personal tolerances and requirements and well worth the trade-off for the better carry option. Its not to Henry so he says he won't do it, and I respect that. But I've got a bezel-clipped HDS in my pocket again today and I'm not the least bit worried. Its still one of the most robust and reliable flashlights I own, even if its ever-so-slightly "lessened" somehow compared to the unclipped masses.
@Hogo, that black SEAL bezel is fantastic. Love it!!