My pots are only 12 cm tall and 14cm diameter across the top. So fairly small. I don't know if it's better to transplant. I was just worried that if I did they would grow too tall, however I could have got away with it actually. So I would say go for it and transplant. And then just keep the horizontal level of you lst down and allow for room when those big ass colas of bud shoot upwards. You will find what works for you. Oh one thing, I can't look back through ya journal atm, how many plants are you growing under your HPS at a time? If it is just the one then transplant it into a bigger pot. I actually have 4 plants but there is only enough light for three, the forth gets neglected. So three plant max will do you well.
Don't worry bout the questions. You should see my journal. I have had to call for help many a time.