Thanks for the quick reply!
How do I know when to switch from veg to flowering? I've read that the plant itself doesn't grow much taller when flowering, but does fill out a lot width wise, and since I'm growing in this small space size is definitely an issues. I'd say I could probably let the plant get 2 feet tall, but I'm hoping to implement some hardcore LST tactics to help me out.
In general, the earliest people typically switch to restricted light flowering is when the plant is sexually mature at about 3 weeks after germination. When that happens, the plant usually shows "pre-flowers" or single flowers at the leaf-stem nodes. It may also switch from paired leaves on the stems to alternating ones.
In your case, where height is a limiting factor, you might run the ENTIRE grow from seed to harvest under 12-12 lighting. That will minimize vertical growth during the vegetative/pre-flowering phase to help keep the plant as short as possible.
I'm not sure exactly what you've read, but typically plants will double in height (and in some cases TRIPLE) after flowering is started. That's the famous "stretch". At some point thereafter, they settle down and won't grow that much more in height, but if you wait until your plant almost fills your box before flowering it, you're going to have a problem!