Just spent the last hour or so looking on Google for the MG mount in period photos . Did find a couple but very indistinict and small pictures , not worth saving . Most interior pictures of presurved late ( 42 -45 ) kubels show the 4 rifle mount instead ( don't see how a AA mount would work there )
I wonder if the MG mount was an early 1940s kind of attachment ,most vehicles , Horch , Krupp Boxer etc had some sort of a AA MG mount during the invasion of France . Hmm , guess its time to pick up another Haynes book