I would grow one plant and use LST and put her in a 3 gallon. Search LST and you will find what I am talking about. You just tie branches down so that other branches get light. In the end it ends up looking like one plant has five or six main colas, possibly more, really depends on the grower. I would get a 150Watt HPS for that space, also get yourself a 10' by 10' thing of panda plastic (for light proofing and light reflectivity, also get yourself some ducting so you can make vent holes in the panda plastic. If you need more help let me know.