I have a AHsupply's 55 an 13 watt bright kits. They don't need all that much clearence. I was origionally planning for it to be 6" high, but I would need to get a second birch 2'X4' for $12 more dollars. I really didn't want to have to spend that much more just to use a tiny little piece of it when I could just make it 4 3/4" and use the one piece. It sounds like that will work though.