diaper question!

I coupon a lot and there's a great promotion coming up on diapers and I want to stock up . Which sizes and how many should I get with twins ?? As of now I have 3 newborn boxes , 2 size 1's boxes and 1size 2 boxes . The promotion will consist of me getting 16 boxes so I need help dividing them up . Thank you ! 
Thank you everyone, you guys are so helpful !! 
I also posted the deal in one of the comments so look for that to also get the deal this week !!