Peabrain...

Funny name. Hmmm/....

Anyways, I thought about that (and I'm sure you and me aren't the only ones).
The reasons I was given against this idea is the fact that mirrors are thick... thus, they'll accept a high quantity of heat... thus, they'll be really, really hot. Really really.

I commend you, because you asked... and just as was done in my situation, I'm giving you "experience's point of view". But I'll tell you... I recently received a 25' roll of Mylar... Dude, forget about the mirrors. Mylar is trully mirror like... it's thin... relatively tough... you can work it and cut it more easy than mirrors/glass....

Nothing, trust us... Mylar is the way to go...

Bottoms up!
-turtle420