How to waterproof Carclo triple optic?

So I'm designing my own headlamp and wanting to use Carclo triple optic. However I'm a little unsure about how to design a waterproof seal into the face plate with this optic.

As you can see in the schematics, there is absolutely zero clearance/overhang to lay an o-ring and clamp the face plate onto without blocking a good 1-2mm of the outer edge of the optic cones. I may be being pedantic but I'm assuming that this would have a significant negative impact on the efficacy of the output and beam, but maybe I'm wrong?

The only thing I can currently think of is using a ~22mm AR Glass Lens with a 1mm thick o-ring x 20mm ID and 20mm ID face plate hole to seal it all up without blocking any of the optic cone. I'd just rather not use a lens if possible.

Does anyone have any ideas for me? Or maybe just some reassurance that covering 1-2 of the outer cone won't effect the beam?!

Small o-ring on the top works fine. Here is a photo of the new FW3A. It uses glass lens with about 1/3mm o-ring. Beam is fine. It's a triple, so you don't get a perfectly defined round beam anyway.

I've just installed a Carclo 10507 in an Ra Twisty.
The bezel cuts of at lest 2mm of the diameter, if not a bit more,
I've also used the stock lens with an O ring between it and bezel.
I have no concerns about losing a tiny amount of light, and you will find that the optics aren't particularly robust. I'd much prefer it safe behind a glass lens.







I cleaned an optic the other day as I'd smeared thermal paste over it. I used Isopropyl Alcohol and it turned the optic cloudy.
All the Oveready triples I have seen have had a lens in front of the optic.
P

Perfect, thank you for the replies and photos, definitely puts my mind at ease. I'm looking at making a few of these headlamps for other people so it probably is a good idea to use AR glass lens for durability based on your comment about going cloudy.