I'd say you will average about 4oz per plant which equals 10 to 11 lbs total. That's provided all the clones make it through flower. By limiting the root size in the 5gallon container you will be limiting your yield. The plants that average lbs each are grown in huge holes dug into the ground and have had the soil supplemented with a quality potting soil/coco cir/soiless mix and a high quality nutrient solution.