The graphics for the wing guns are not ordinance like the gondolas on the 109s. Like the 50s on a Pony D, The 2 guns do not disapear when you chose 4 guns.
The weight of the guns and the ammo for them is removed from the model though.
It would be nice if the outer guns were modeled as Ord that disapeared when removed or changed to shorter barrels when you took the 30mm of the A8..