Thank you, Bob, for playtesting. I think that Spitfires you attacked were over rivers what gives them 0,5 additional defence points. Otherway Me-109 and Spitfires are virtually equal - both have 8a/8d points. When you discover FW-190 (11a/11d) you will get upper hand in air until the arrival of American planes.
Yes all "stackable" squares give double defence too (but not against air attacks!). It has been taken account in unit stats. Most units have their attack 2-3 times stronger than defence. Also forests don't give additional defence bonus.
Yes the SS shield is too up. I didn't noticed it
I have tried to make the scenario this way that AI don't have any advantage in unit strenghts. When you play Allied and Soviet versions then you have exactly the same units as they have now (NKVD, Polish Infantry etc).
SS Troopers are roughly equal to NKVD:
NKVD Troopers - 16a,9d, 5h,5f
SS Troopers - 18a,8d, 7h,3f
And Spanish Legioners (Axis gets these in July 1941) to Polish Infantry:
Legionaries - 16a,10d, 8h,3f
Polish Troops - 19a,8d, 7h,4f
I think that the problem is that these elite infantry units are balanced for 1942-43 (their strenght is the same during all the scenario and
this reason I balanced them for middle-war years). It means that they are relatively very strong in 1940-41 and too weak in 1944-45.
Tracid, you gave good idea for solution: I'll make all these elite infantry types evolve with time: weaker at the beginning and stronger at the end (of course!
).
Also I try to "calm down" the AI bomber building. They really build now too many bombers. When I finish with the new version (1.8), I'll send it to all playtesters. There are quite many surprises what I think you like (I hoped to save them for final release, though).
Oops, I didn't know terrain was a factor influencing air combats... 
