Greetings all,

I purchased a nice sturdy sheet of Mylar at an art supply store some years 
back. I used it to make some Christmas tree ornaments and then stashed the 
rest in the closet. What was left was just right to line the inside of my new 
hood. This material is a coated sheet of plastic, with mirror-like surfaces on 
both sides. It is fairly thick (I had stored the stuff rolled up, but it 
popped out nearly flat as soon as I pulled the rubber band off) and is 
definitely stiff enough to hold its shape quite well (better than potato chip 
bags ;-). Yet it is very easily cut by scissors. You might want to check this 

Happy building,

Christine in Palo Alto, sunshine and flowers everywhere