With 92 watts, you could TRY drilling some holes in the top of the box and on the sides at the very bottom. The hot air off the lights will rise out of the holes and cool air will get sucked into through the bottom holes. Im not sure if this would be enough ventilation however.
If your struggling with cutting a hole in it,drill loads of 4mm holes 3 mm apart in a 12cm diameter circle, then screw a pc fan to the inside of the box so it pushes the air out of the holes. I have this done on top of a wardrobe and its keeping 150w of cfl cool enough. I also have a black foam ontop of the holes to stop visible light escape although this does reduce the airflow.