Just one light in a 4x4 isn't my preference. I would much rather have two lights, even is less wattage than one big wattage light, for a better light spread. I have two of the Spider SF1000 in my 2x4 tent, as well as some Autocobs. Each plant gets their own light. I've owned a couple of 4x4 tents in the past and the plants each got their own light in that tent too. Have you checked out the Autocob at
www.cobshop.net. They are great lights as well.