Question about glass for a DE halide fixture

So, the protective glass cover broke (again) in one of my 250watt metal halide fixtures......No tempered glass replacements are kept on hand in this size at any of the major places that I could find, all would have to special order and it would take over a week for it to get to me.  I didn't want to run the fixture without the glass, but that means half my tank is unlit at any given time (I've been moving the light back and forth).  I got some UV protected glass cut to size at Hobby Lobby today and was going to use that, but it is not tempered.......I was going to cut some eggcrate to fit over that side of the tank (between fixture and water) to minimize any splashes and avoid breaking it.  
Now I'm wondering if there's any difference between the tempered glass in regards to temperature and this UV glass I got from Hobby Lobby?  We're headed out of town tomorrow and I'm a little worried its somehow going to burst from the heat, although I don't know that for sure just wondering if anyone has any knowledge about this?  /DesktopModules/ActiveForums/themes/_default/emoticons/crazy.gif

 

So you both have tried this with a metal halide fixture made for a reef tank? Everything I have read online says it *should* be ok, as long as there is no quick temperature changes, or something like the tank water hitting the hot glass. The tempering apparently does nothing to aid in withstanding heat, just that it breaks into chunks and not shards......this is just from reading online. My husband says it should be fine and he works with glass somewhat, but just thought I'd ask and see if anyone had first hand experience trying it.