No you dont man, you have no clue do you? My last set up I had was a 6 x 3.5 x 3.5 with the perfect set up with a 600watt hps, 500 cfm intake and exhaust, humidifier and a 10 liter displacement CO2 canister with just regular nutrients and superphosphate and out of my 3 ak47s combined gave me in DRY weight 3.25 pounds of BUD not leaf, bud. The key to harvesting every 80 days that much weed is by having separate grow chambers, one for germinating and one for vegging, so there is always a plant germing always a plant vegging and always a plant flowering. By the time your flowering plants are done then your vegging plants should be ready to be put in the flower oven and the same with germing to vegging. I have already figured out how to easily produce 5 pounds every 80 days about(rough estimate could be less or more time). Im not trying to sound like an ass by arguing but im just trying to say that yes it is possible, and you should not just go doubting watever a person has to say im right on this one; because I have experienced my plants capabilites and obviously you have not.
It is true that the plants will stretch a lot while flowering, you must have and out look at whats going to happen so you do not burn or starve your plants of fresh air and CO2.