Quote Originally Posted by kmckelvin View Post
If you stack the second layer as 9x9, you won't be using all of the available space, surely you'd have to take one sphere off both sides and pack 8x8 to be optimal?

How do you get the height of 1.541196cm given the 9x9 packing? I tried finding a method to work that out (without diving into all kinds of trig that I haven't touched since school) and went for an easier option instead.
Ignore me, it clicked. Still curious about the 1.54 answer though.