Heres a technique I use to decrease AI 'accuracy' on certain units. Use invisible Armored targets (you can find them in BAS's Tonali/OPFOR addon or by themselves on the BWM MOD's site{If I remember correctly[which I usually do
]}) . You can use a simple script to cause a few of them to randomly 'hover' around the target vehicle in 3 dimensions, so there is a good chance that the AI will target one of the invisible targets, giving the appearance of a near miss.
It actually works rather well, and there is even a chance that you can 'unintentionally' be hit if the invisible target ends up between you and the AI. I found that 3 per vehicle in a random 50 meter hemisphere works pretty well. Best of all, you dont need special high dispersion addons or extremely complex math.
-Grendel
ps I hope that link on the reply above mine did'nt already bring this solution up....