In a 4x4 if you spread the canopy to match the foot print within a foot thick of canopy and the help of some training technic to spread conopy evently and the minimum 600w power of hps you will get 1lbs + with 1 315 cmh yould be right around that pound more ir less will depend on how you train. And if you remove all useless shoot that will produce insignifiant bud sight so energi can be focus on the upper 12" of bud sight after 3 week of flowering.. On week 4 of flowering the only bud sights sould be within 12" so your traninn should consist of having all or as much has possible all tops on same level during first week of flowering (lowering top spreading sight evently) and gave everything undesurable remove '' useless bud sights" and leaving atleast 1 feet of leaf below but sight. Remove everything below that line atleast 1week befor you put into flowering. Its a question of foot print and density with a period of healing to promot flowering within a certain distance. Most people e prefere growing many plant and flip em once they fill that space.. But it is achievable even with just one plant if you are patient enough to veg this long. Genetic can greatly speed up this phase by reducing vedge time. But all plants can be trained to achived 1 pound with in 1m square foot print. Not many genetic fall under this but some are in lower yielding genetic for sure and the only way they can yield it is with a great air flow to deal with overcrowding.... Good light good flow and good traing. Don't forget to double up on pot size.. Bigger roit system better life support...