As to the question of the value of keeping a Large metal Flashlight in your vehicle.
Beyond the obvious of having a light, having a way to break out/in glass if needed with an accident
and a way to defend yourself against people or even wildlife(Yes it has happened down here on the trail at night to people I know)
Legally in many States/Cities/Counties/Provinces whatever, a MagLight or large FlashLight is NOT technically considered to be a WEAPON, and so it can be kept in the Vehicle without permit or question. But baseball bats, Ax handles, batons etc can be.
I also agree that having one sitting unrestrained in the vehicle would leave it free to bouncing around some when you get into the dirt or potholes. Mostly annoying, partly dangerous
And also I'm leery of one of the larger ones hanging up over my head held in place by clips or velcro when offroad jolting was going on.
here is where I mount mine and when there is no top i take out the light unless I think I might need it. and I happened to buy a maglite bundle at sams club for $15 came with a 4 cell maglite and a AA maglite and this mount.
I prefer Pelican Lights. Explosion proof lighting is required for work, and these are the best I've used.
I use the same mounting spot...works wonders, its right there when you need it, but also doesn't get in the way at all. I also like that it literally takes no time to do, just take the screw out, and screw it back in haha
Go to the above link and read the first post for the basics and then read down a few posts until you get to "Whiskeypete" comments. I just did this today based on "Whiskeypete" improved process and it was fast and simple, but most importantly it looks OEM!