Yes Lazs.. that is what they are saying. Yes Lazs, they are also right.
Even the Panzer IV, which wasn't all that heavily armored, was armored heavily enough EVERYWHERE to stop .50 caliber or 20mm Hispano (unless the Hispano had AP rounds, which none did in Europe), and Mg151/20 rounds (which seems to be modelled correctly).
I posted about this in a different thread a while back, and Tony Williams was kind enough to respond with exactly how much penetration a 20mm Hispano, 20mm Mg151/20, 15mm Mg151/15, and 12.7mm .50 caliber API round would have. For the 20mm rounds and the .50 caliber, the result was less than 13mm (I believe the exact range was 7-13mm, with the lower numbers being more common) of armor, under IDEAL conditions. Ideal conditions (and I asked) are zero sloping (i.e. the bullet hits at a 90 degree angle to the armor), and a range of less than 300 yards. The only places that had less than 13mm of armor according to the sources I checked were the top decking of the hull, and the top of the turret. The decking was not sloped, I think the top of the turret was marginally sloped.
So, for a plane to have a CHANCE of penetrating the armor, it would have to be in a vertical dive and less than 300 yards away from the roof of the tank. So, to answer your question, your typical U.S. plane with the .50 caliber API rounds WOULD have a chance at actually 'doing something' to the tank, it would just end the strafing run as a smoking hole in the ground.
As far as the .50 caliber (or anything else of any caliber less than 23mm), you SHOULD be able to knock out the tracks on the Panzer. What you should NOT be able to do is hurt anything else.
The M8 is even worse in my opinion. The Panzer at least (for me) can take a .50 caliber strafe for a few runs before exploding, the M8 will go up after a single run, every time.
The armor model for the Panzer and M8 REALLY needs to be looked at. The good news is that I think HTC has it on their list, because it has been such a prevelant complaint for a while now. Besides, Aces High is a game about airplanes, not tanks. Even though tanks are in it, I'd expect them to play second fiddle to the airplanes, and their problems are naturally of lower importance than a problem with one of the airplanes. They'll get to it when they are able, I'm sure.
EDIT: I remembered it wrong. The Hispano could penetrate a maximum of 20mm at zero slope from 200 yards. The 5-13mm range is for a 40 to 60 degree dive from 300 yards away. The .50 had similar stats in both categories, with the Mg151/20 being worse and the Mg151/15 slightly better than the Hispano and .50.