I believe that I may have discovered why the PzKpfw IV appears to be so brittle when fired on by aircraft and Osties. Yesterday evening, I was driving a PzKpfw IV, and while I was on autopilot on my way to attack a base, I idly flipped from position to position. I noticed that the hull machine gunner position, unlike the driver's position, had a default head position up out of the hull, as if he was sitting with the seat raised all the way.
When I looked back, I saw something amazing, that absolutely blew me away -- I could see into the turret:
There is a gap that looks big enough to stick my hand into between the bottom of the turret and the top of the hull. If the polygon data represents the actual collision surface of the vehicle, then any HE shot that landed on the hull deck near the turret would get its blast effect passed into the interior of the tank, bypassing the armor completely. Similarly, machine-gun rounds striking the upper hull at the right angle could be deflected into the interior as they bounce off the upper hull armor.
The Ostwind, in comparison, does not have this gap between the hull and the turret:
If it's possible for damage to blow through into the tank through the gap between the hull and the turret, then it stands to reason that the PzKpfw IV is going to die easily to attacks from the Ostie and aircraft, when it shouldn't historically.
