Flexwatt controlled by a thermostat will not melt plastic. I'm not an expect on the subject but I think most plastics have a melting point of 150+ degrees, so unless you have a thermostat malfunction you don't have to worry.
~*Rich
1.0 100% Het Albino
1.3 Normal
1.0 Spider
0.1 Mojave
1.0 Pastel 100% Het Goldfinger
0.1 Pastel 66% Het Goldfinger
0.1 Pastel PH Goldfinger