No plastic - just regular window glass is fine. Melting point has nothing to do w/ it. It's all about stress, expansion, contraction...
A single 96W PC bulb is quite enough to crack a glass top if left too close. If you put 2-3" between glass & lights, you should be OK.
One more consideration - if you have a black plastic center brace, lay a layer or two of white plastic (like grocery bag) between it & your lid. This will prevent overheating of the center portion of your lid.