Vehicle Barriers in Garage

My question regards when the ASCE says 6,000-lb force acting between 1’-6” and 2’-3” at a max of 12in by 12in. For a retrofit cable barrier, say I need 3 cables… i am suggesting that if the cables were at 18, 22.5, and 27 inches this would not work because the 6kip load acting at 18 inches high would be acting through the center of the 12x12 square. Am i understanding the 12x12 square correctly, i realize it is mostly there for punching shear but it would seem that the square would also apply as the largest impact area for cables. So if you had cables spaced at 4 inches and one was at 18in, one at 22in and 26in, the one at 26in would not be engaged so you would need one at 14in. Again this is for retrofit, assume pedestrian guard and the 33-inch requirement for 1-foot vehicle drop is satisfied.