Are you air cooling the reflector?
For what its worth, i'm not going to say this will or won't cause a fire because thats too liable, but I will say that when my fan is going for the reflector I can put my hand on the glass, the metal frame, every square inch on the outside of the reflector and not get burned. I also have a 600w cooled by a 240CFM axial inline fan.
So if its not burning my flesh or my plants, i don't think it'll burn wood or plastic.
If you're concerned look up the burning point of wood and plastic. I'm sure you could do a quick google search. My guess is its not going to melt or burn anywhere under 120F and if your reflector is getting that hot you're in for a lot of other problems.