It's neither bad nor good, it depends on your overall situation and goals. Straight to 12/12 from seed will reduce the yield per plant, resulting in one main cola and little if any side branching. But, this approach also is the fastest from germ/clone to harvest. In a SOG (sea of green) grow, you do exactly this, and pack plants in tightly so that your yield per plant remains low but your yield per sq foot is still strong. If you set up a cloning operation you can generate all the seedlings you need and just keep sticking them straight into 12/12.
get it up to 14 for twp weeks that will rise your chances of getting females.. then after that go with anything above 18 hrs
good idea if u dont have 2 rooms,i keep around 20 to 25 plants packed tight together under a 250W HPS cooltube half in veg the rest are budding all in the same room suits my purpose well letting me keep bud going,only thing i noticed they veg a little slower under 12/12,an yes yield dose go down per plant.
youll end up with about 1/3 or 1/4 of what the plant would of gave you had you vegged it for a reasonable time.. same ratio when considering the finished size of the plant. still , If you do it right i dont see why you wouldnt pull an oz a plant. basicly like turning 12/12 strains into auto's.. problem is.. if your growing a strain that lets say takes 9 weeks to flower. Its not gonna be done from seed in 9 weeks under a 12/12 light cycle ...