The dimensions on your box may be a bit small. I'd suggest going with an autoflowering strain and even then you will probably have to tie colas close to the center cola as they'll wanna stretch out sideways (unless you rock out the party cups). For reference I chopped an auto out of my garden last week that was about 16 inches in diameter. Good luck man, size constraints aside, looks like a dope set up for a one plant op.