Well it depends on how big the plants are. You could consider keeping a mother plant under 18/6 Vegetative state in one room, and your HPS at 12/12, and doing a little mini sog or scrog. I would put maybe like 5-6 rooted clones under a 150 watt, and if the mother plant is sexually mature, then the clones will be sexually mature as soon as they root and will be ready to flower regardless of size. This will grow a small christmas shaped plant and you should be able to get 1g per watt.