The Billiard Congress of America defers to the World Pool-Billiards Association for the definition of a proper 8 Ball and 9 Ball rack.
According to the World Pool-Billiard Association, a proper rack for 8-Ball is:
“3.2 Eight Ball Rack
The fifteen object balls are racked as tightly as possible in a triangle, with the apex ball on the foot spot and the eight ball as the first ball that is directly below the apex ball. One from each group of seven will be on the two lower corners of the triangle. The other balls are placed in the triangle without purposeful or intentional pattern. “