if I understand correctly, you're using 48" fluorescent tubes, correct ? ... if so, keep in mind, fluoros do not 'penetrate' the canopy, meaning you will need to keep the tubes within an inch or two (max) from the tops of the plants (I hear the T5s penetrate better than the T10s I used for years, but I doubt they're 'that' much improved) ... you will likely have to raise them daily ... you may add horizontal tubes midway down the plant, but I personally didn't see much advantage to vertical tubes, too hard to keep the distance correct ... just burn as many tubes as you can, ABOVE the plants, and keep them close to the plant tops ... be sure to use a good oscillating fan in there, too ... good luck :thumbsup: