what kind of lighting are you using ? what's your lumens per plant to yield 2 oz . per ?
I'm using a 400W HPS from start to finish. I bought a 10 pack from Dr. Chronic and started 5. Grew those out, harvested some pollen, and ended with 2 beautiful ladies, one with a little over 2 Oz and one with an 1 & 1/2Oz. About a month before I cut, I threw in the other 5 and got two more ladies, one of which I'll pollinate a branch for seeds and grow a few more than just 2 at a time.
Size can vary from short and stout to this monster I'm currently growing. I'm not sure about lumens per plant but I keep that bulb within 5 inches of the biggest girl.
I would never buy the fem seeds if you plan on doing lots of these. Seeding is the only way you get to spread the favourable genetics.
I also use Fox Farm, just the trio of nutes. They seem to love that juice.