Getting back to the topic...
Let's put away probability for a minute and consider logic. Let's assume that both enemy and allied tanks facing each other are identified, assume any distance, penetration and armor thickness and also assume that the angles of penetration are not a factor due to a tank being in a hull-down position.
A tank gunner firing on a tank which is not hull down has the option of firing at the turret or the hull. If the opposing tank is hull-down, the choice is only the turret.
If he knew that firing at the hull was not advantageous, he would ALWAYS (unless, possibly, a conscript with no training) fire at the turret. Thus, the kill probability upon both H/D and not H/D may - at best - be equal, but there cannot be an advantage in avoiding a hull-down position. Gunners would simply fire at the turret if there was a disadvantage in firing at any other part of the tank.
(Others may say that hull-down should be better protected - and I agree - but my point is that a hull-down tank should never be at a disadvantage under the assumptions made above.)
I am not sure whether or not this is a REAL problem as I have not seen the "Studies" and experiments, but if it is and relief of said problem is not a burden to the fine designers of CM, it would be nice to see a correction.
Please respond if you have a question or a comment to my tedious post. Thanks.