I grew in that same closet for a while. 2x3x8. I put a plywood divider at 3' so I had a 2x3x3 T5 veg room and a 2x3x5 400hps flower room. You will need to be air cooled and have a 6" 440cfm or better, but it is possible. During the summer I needed to have a full time exhaust going so 2 good fans...