Reptile heat pad

Has anyone tried using a "reptile heat pad" in lieu of heating coils in the
substrate? I had not heard of such a thing until the local store showed me
a long, thin plastic strip. It's about 5" wide and comes in segments about
6" long that make it look like film. Each segment is a 5w heater and the
segments can be cut off to adjust the overall length of the strip.

The film  is flexible and can be rolled up when not in use. It can be
plugged into a rheostat for control. The storeowner said to position it
outside and under the tank, either taped to the bottom with electrical tape
or resting on slate (or the table top or other material) under the tank

Greg. Tong
gtong at sirius_com

"Every infinity is composed of only two halves."