Hmmm. Since the last tank armor change I've found that straffing PnZ IVs is a complete waste of time in anything short of an Il-2, even then it takes me multiple passes.
In my nominal ride, the quad Hispano armed Mosquito, I have had no effect unless I come right at the tank's rear with my props practically mowing the grass, eg, as low as I can so that I have as close to a 90 degree striking angle with my rounds on the rear hull armor as I can get. Even then it takes about 600 rounds (almost all of the Mosquito's load) to destroy a single Panzer IV H.
I have't seen a single pass gun kill on a Panzer since the changes introduced with the Tiger.
On the other hand I have had Panzer's one ping my Mossie with the 7.92mm, despite the pilot armor.