you can try plexi or acrylic. instead of one piece use two pieces and make a sandwich out of them with a 1/4",3/8" airspace in between to act as an insulator. kind of make a window in the door with that.if the box is sealed tight one 4ft strip of 11" flexwatt should be plenty to heat that size. i would run the flex on a helix. and use a fan at the top to move air. the 4" 120volt fans at radio shack work good. i don't know what would be better than water jugs as a heat sink or thermal mass.



vaughn