For me this question is a little hard to answer without knowing the grow method, hydro or soil. My personal preference is to grow 4 large mature trained females. Others might say SoG style and that could be up to around 25 or more. If this is a soil grow, I would certainly do 4 larger plants, less soil to move around and water. If it is hydro, then I'd still say 4 but but you certainly aren't limited to that. My opinion is at most do 9, 3 rows of 3 but even at that they will be fighting for grow room pretty quick, they will require more training and trimming to get full potential. Starting out with a Sea of Green style grow will be difficult, depends on genetics, light, and just general all around grow conditions. Go with 4 and switch to 12/12 at 12" - 24". An added benefit of larger more mature plant is sexing, you can often see preflowers on a older plant and determine if male/female before you go switch the light to 12/12. My .02.