Primary safety concern is the heat output. Plus, anytime you change the design on something like that, you are creating a safety hazard.
That said, I've read numerous articles on this, and have yet to hear of any mishaps.
I've often thought it would be neat to experiment with this. I do have an extra cheap light strip around. I'd like to know just how hot the bulbs get. My Current CF setup gets hot too, and that is in a partially plastic unit.