I once grew in a 3'x4'x8' closet in my bedroom with a 1000 watt halide. I had a 265 cfm blower sucking air into the attic and cut a hole in the floor that pulled in air from under the house. Must have been 90+ degrees in there but man it produced.Yes, just make sure you have Great ventialtion, it will get really hot being in an attic.
But yeah, that's a good size light for the space