This is my understanding ... "Sandwiching" flexwatt is against the manufacturers suggestions for safe operation and if there were to be a fire, damages would not be covered by insurance if improper use was discovered.

The compression of the central component in the tape (resistor) causes tremendous heat build up which can be combustible. I know first hand of at least one rack that went up in flames from incorrectly installed flexwatt.

While today I do use flexwatt exclusively for heating my racks, when I had enclosures (melamine, wood, PVC, etc) I used to use radiant heat panels to heat them. After years and years of trial and error, RHP's were the product that I found that heated the enclosure most efficiently and unlike my other types of heating elements were completely safe to the touch. I have experience with many different brands of RHP's, but found the Pro-Heat panels from www.pro-products.com to be the best in the business.

Hope this helps.

-adam