Lightweight, Weapon-Mountable Flashlight

I know very very little about flashlights and/or how to build them, but I've been looking for something like the Quark 123, Fenix PD20, in size/length and output that is able to withstand the recoil of an AR15 (which isn't really that much recoil).

The manufacturers of both the above-mentioned lights said they weren't able to withstand the recoil of a firearm. Were they just playing it really safe for warranty reasons, or should I follow their advice? I had a TK12R5 mounted on my rifle through a couple hundred rounds that never had any issues, and it's not stated as a weapon light either.

I've read that what makes a light weapon-friendly is having a spring on both sides instead of just one. With that in mind, would I be better off building/piecing together my own little light? If you guys think that the Quark 123/Fenix PD20 type lights will work fine, I'll grab one of those...but I do enjoy building things myself, and if you experts think that could be a better route, I'll put up some criteria i would like and see what suggestions I get from you all as to which parts to go with.

Thanks!

Peak LED Solutions lights are the only lights made that the electronics compartment
is filled with epoxy, this withstands several thousand Gs of force. The Night Patrol and
First Responder series come with a one inch diameter body in the 2 x CR123A, 3 x CR123A
and the 4 x CR123A battery compartments. USCSOG has used them on their 12 gauge
shotguns for over a year.

Curt

The recoil might confuse a PD20 into thinking the button had been tapped, and cycle to the next mode. Not something you want your weapon mounted light doing.

Why not just get a dedicated weapon light?

AR recoil isn't that bad. I have run a variety of lights on my M4 and never really had an issue. I did discover pistols to be another issue. I put together a weapon mount light a few years ago that works well on almost anything. It is picatinny mount so AR rail mountable, or as in my case, duty M&P 45, and originally on my 870 shotty. I took a LEDwave weapon mount light and dropped in a high output P60 drop in from DX. This light has multiple modes, high med low and strobe, and has enough throw for medium AR work. It is stunningly bright so works great on the pistol, and has yet to malfunction despite seeing hundreds of rounds of 12 gauge, thousands of 45 +p duty loads, and a lot of 556. It also works in my Swaziland ALS holster which wad dedesigned for X200 I believe. Just had to knock out the dirt plate on the bottom of the holster and replace with a different homemade piece. I will try to post pics tomorrow... I have less than $100 in it, and it has never failed me... A lot of guys in my dept had me get them the same setup shortly after. BTW, I am an M&P armorer and Firearms instructor.