Judging by its size and the size of the growbox, I would advise translating it into flowering. after switching 12/12, it will start to grow much more actively. and will roughly double in size before it stops growing and starts to get fat.

Hey man, your plant is looking great. It is up to you when you switch...Depends on the space you have and how much she will stretch in flower....Some stretch double the size in flower. She looks mature enough to start flowering but like I said, its up to you. Good luck and happy growing