I'm guessing you have a full ceiling to work with? You should be fine letting them grow as is if you do, and you're going to start flowering next week.

I've seen mine do some good stretching but well within limits. Not much bigger than 3' or so.

Topping rocks, for me it's going to increase yield a lot as my plants grow nice colas from the stem and 6-8 branches and little else.

Are you going to take some cuttings before you flower?

P.S. - I pinged you on facebook, hit me up