On one night in particular I kept upping that IID trying to get a kill with it. My experience was much the same as Krusty described, with lovely orange fireballs erupting on the deck above the engine, and yet the tank waltzing on as if I was firing .303s at it.
It was a frustrating night to be sure. Made me think it was some kind of rubber bullet syndrome.
Regardless, I've found when I fly the IID, it is more dangerous to me than my target. Yes, I am certain it is the pilot and not the plane.