I would not top it personally at this stage. You can tie it so the top shoot is lower than a couple of the side nodes and the effect will be similar. I fine that topping a plant too far down the stalk frequently allows disease to attck it. Pinching the top growht is perfectly safe though, just pinch off the growing tip, but not if you plan to flower he within the next 3 weeks.
Removing entire lower branches can help with air flow in an overcrowded grow room, and reduce the proportion of annoying popcorn buds that suck balls to trim after harvest.

My advice is to bend it over, not to top it.
stinkyattic Reviewed by stinkyattic on . Cutting back I have attached a picture. How far can I cut this thing back. As you can see, I have 4 Afghani veging with it. It was started about 3-4 weeks before the little ones. Rating: 5