defensive posture

[Havoc]

Let me correct one thing, the skirmishers "screening" ability works only if they are in a hex where the line of fire runs through. That gives -20%.
But if the skirmishers are in the same hex and even if at the top there is no such penalty.

I don't agree.  My observations from the games I've played indicate that there is a bonus for having a skirmisher in the hex on top of a battalion.  The rules state that fire must pass through the skirmisher's hex, not what hex it is in.  If the skirmisher is in "front" of the battalion, the fire is passing through.  If this is wrong, please share the game rule or design notes that state this.