I had an idea for a kobold-operated tank.
The armor would be thick enough to be immune to damage from all mundane projectiles (arrows, bolts, flintlocks, javelins, etc.), and resistant to magic and melee damage. I have heard AC described as "how hard it is to hit you", and due to the size and speed (big and slow) it should have a low AC: it would be really easy to hit but really hard to do damage to.
I however wanted to add hard to hit weak points, like a pair of slits in the armor for the driver and ballista operator to see though, or the tank treads.
My question is this:
Can a target have TWO AC values? One low, easy to hit AC for the main body and a harder to hit but very vulnerable AC for specific weak points?