Why not just use a ceiling fan down rod mount kit, then on the threaded end place an electrical junction box or mount plate then attach the camera directly to that. Another thought - which I have used MANY times for projector mounting in bars or or restaraunts is use black pipe. Use a 1" or 2" flange to mount to the ceiling then screw your exact desired pipe length to that, then on the other end screw another mounting flange on - get a 6"x6" 1" thick sheet of plywood painted or stained to a color of your choice. Drill a hole in the center - now you can feed all your cables down inside the rod and out the bottom, in your case connecting the rj45 cable, inserting it all back up into the rod/flange and mounting the camera directly to the wood mount.