when i split mine, i split it 50:50 to start with, and after 3 days when i knew what needed to be adjusted in which ever direction, i adjusted for... i now take 7 at night and 6 in the morning. (10pm and 10am) i do notice changes in FBS when i adjust my evening basal.
so I would go 50:50 on a 12hour gap to START with... then work from there and see what works best for you
Good luck! You'll hopefully be amazed at the difference it makes! I was...