I understand that when you switch to a 12/12 the plant continues to grow, given 4 feet is the ceiling height, as what height should you switch over for flowering?
between 12" and 18". Your plant will double or even triple in size. Want to make sure you have plenty of room. Too increase your yield, look into LST. Great solution for smaller spaces. Good luck.
Also make sure to account for the 12 inch gap between your HID and your plants canopy if you are using HID.
agree with the above 2 posts. I didnt believe that the plant would grow 3x it's height when going into flower and i found out the hard way, my 20" plant turned into almost 5 ft. and grew above my light. my 5' was bagseed, so it was also hard to know how much it would grow, but at least you know what strain you have