Too Hot?

Do you think a 5 watt UTH is dangerous to put under a plastic enclosure? I let it run for a few hours and then put it under a tester viv and left it overnight. Today it seemed fine and the plastic on the inside wasn't too hot. Is this ok, or should I stay away from plastics and UTHs period?

A UTH with a plastic enclosure is just fine. I use flexwatt on all of my rubbermaid enclosures :)