I would believe that 6-oxo would not close your growth plates off, however 6-oxo does increase the productin of LH and FSH hormones, which are responsible for growth. So 6-oxo might just make you grow taller, however the increase of testosterone and DHT caused by the production of LH and FSH hormones, might cause the onset of puberty like actions within your body. I believe that estorgen is the trigger that closes growth plates.
I would suggest that you do some looking into the effects of LH, FSH, DHT on people your age. Another thing to cross reference is hormonal imbalances and there effects in people your age, which will give you a clue of what is going to happen. Look up hormonal imbalances and focus on subjects with the over production of the previously mentioned hormones.