How long do i leave the lights at 16-8 till i switch to 12/12?

I want it about 10'' when it starts to flower. Does anyone know how big it might get when its done budding?

Before you read this, I want you to realize that I'm a beginner just as you are, but here's what I've learned.

I believe that with a predominant indica, you want to have it 1/2 of the height you intend to have when you finish flowering, whereas with a predominant sativa you want to have around 1/3 of the height. Somebody please do correct me if I'm wrong, I'm learning here as well! You should consider reading a lot of literature on Cannabis, researching (even reading research papers over at Google Scholar, very interesting!) on the internet, and of course, asking. One thing to keep in mind, is that you do learn by mistakes, so if you mess up at least you can learn from what you did wrong, and you can always start over. (That's absolutely how the brain, specifically the prefrontal cortex, learns - from mistakes. The primary problem is repeating the same mistake)

Good luck!

Also a total Noob, but from all I've read so far MOST cannabis plants will double their height or more between the start of flowering period and harvest.

Look into LST training. If your plant looks like it may get too big, start training it sooner rather than later and it *should* be better controlled. :) GOOD LUCK!