Yeah. I'm looking at 48" x 48". I think I;ll have to talk to someone who works in fibreglassing to see how to make a fibreglass sheet that big. I could embed an aluminium sheet into the fibreglass, or just lay the resistor wire between two layers of fibreglass. I was going to use nichrome wire as the heater resistor because its resistance per metre is known, and I can work out the power consumption.

Old Man Emu