I have made a lot of lights for a lot of different folks and ..... IF..... a single one of them had hardened glass in them I sure didn't know it! I think in four years of making custom lights I have replaced one lens for a customer and that was broken during a bike wreck. The customer came out a whole lot worse than the lens. 
A good AR coated piece of glass in my books is sufficient. Just my .07 cents worth. 
Dan.
You and 300,000,000 other folks!
Dan.
LOL, maybe add some zeros.
Cutting glass can be a very hazardous proposition, so I feel some relief that you won’t be doing that and putting yourself in jeopardy.
Be safe, take a breath of those luxurious pines for us. (Mary’s from Mississippi and misses the pines dearly, we’re in farmland, no pines)
Odd, I never saw this poll hit the front page (or just never noticed?)
Hardened is always better else I have more glass-broken flashlight now. Now my ultrafire glass is broken, put out ugly beams.