hi there, i've been reading your post and have some comments to make.....ok here they are....

1,5x1,5=2,25 sq ft....that's plenty for one plant only, plus with your light of 250hps you get around 111 watts/sqft which is like heaven for plant growing....as for when to throw it into 12/12 do the following.....let it grow for one more week and then tie it down (LST), what you're looking for is to make a bush type plant, the reason for that lies on the limited light penetration your bulb of 250 has....obviously if your plant grows taller than 4 ft , your light will not be able to reach further down below considering the fact that it has to be already at a safe distance from the top of the plant.....if you LST it, you will be able to stimulate growth from the medium/lower branches and you will be able to control its' height....a large bush will grow with bud sites everywhere you look....also you can top it once or twice be fore 12/12.....by doing these two techniques (topping and LST) you will be able to be into 12/12 cycle within a month or so from today....the final yield though will definately be much much more than 2 oz....what you're looking for is many small to medium sized buds as you need your light as close to the entire plant....anyways, if you're only after 1-2 oz you can avoid doing any of these and go into 12/12 within two weeks from now or when the plant passes the 12 inches of height....remember, you can apply LST even during flowering but topping it takes place only when in vegetation.....