You already said what I would have said. I would say to put a couple of bends in the ducting. If that won't work, is there any way to install a deflector of some sort on the outside of the grow chamber? If so, you could aim that deflector away from the light source in the room, eliminating MOST of the light. I would post a pic. Post a pic and someone will immediately be able to look at your setup and tell you what you need.