In a game I just attacked an opponent who got a +32 AA bonus thanks to a Ranger + a horde of items!
This bonus combined with the regular stack bonus (leadership/morale/walls) to turn a 15 strength Ghost into a 65 strength unit. So all units in this stack got +50 strength (it was an all flying battle) turning what should have been a win for me into a loss.
This is a bit over the top. The stack AA bonus PLUS the regular stack bonus (leadership/morale/walls) shouldn't exceed +30 (the game cap). A units individual AA bonus should still add onto that +30 (just like the terrain bonus's do).
KGB