After some more testing I found out the way you place/ position it is super important for some reason. With gun barrel facing down (so front of tank is higher than back, it misses 95% of the time.)
When gunbarrel is facing up ( front lower than back) it hits like 95% of the time. Can this be a bug? 
In the video in this topic you can see the barrel is facing down. Its on a hillish part where fron is slightly higher.
COH 2 Science!!, im eager to hear more
*As for the KV-2 Penetration, i have never seen it bounce its shots on SIEGE MODE, so i think it might have 1000 penetration on it, like all howitzers*