My green circuit array I use in early game when only one belt of circuits is needed. The blueprint is for 6 groups of 3/2 ratio sub-assemblies, which is one assembly over the 15 items/sec capacity of yellow belts in 0.17. I've found that the extra sub-assembly helps smooth out input bottleneck shortages in early game. This should be easily expandable for red and blue belts by extending it out to 20 assemblers for red, or 30 assemblers for blue, if you stick with it.