Recent research discussed in Harvard Business Review suggests the optimal size for a decision-making group is seven. Each additional member added above seven decreased the group's decision-making effectiveness by 10%. Mathematically think 0.9^(x-7) for x>7.
Jesus had 12 disciples, but I'm not sure they count as a decision-making body. And I'm not about to question the plan.
My comany has a 12-member board of directors. I'm not questioning that wisdom either. But might their decisions be only 59% of their potential? That's almost like having half your brain tied behind your back!