I see all stugs are armed whit a AAMG ingame (version 3.00). Now i have never seen or heard of this. I know stugs carried a MG-34 or MG-42 that could be sticked trough an armored plate infront of the loaders hach on the roof superstructure, but an AAMG it was not...
It could not even shoot anywhere but the front sector and for any other shooting the loader would have to remove it from the armored plate and shoot from the hip so to speak.
It's just a hole in the armor plate whit a LMG sticked trough. Better weapon to simulate it would be a LMG or BMG.
This is a good pic of one you can even see the MG's bipods extended.
Heres one showing a restored stugIII from the side:
The late model StugIII had a remote operated MG where the loader did not need to expose himself other than to reload the weapon:
The picture is showing just the remote mount and not the MG attached to it...