The rear reverse seat wasnâ€™t placed there for an MG, however in the latter years of the war, it may have been utilised as an ant-aircraft spotting seat, there again just because I havenâ€™t seen any photos of an MG mounted on the rear, doesnâ€™t mean it didnâ€™t happen. All the photos I have seen, show MG34â€™s deployed on AA tripods around the unit, to add to this, memoirs talk of soldier abandoning the vehicles for the nearest ditch with their rifle.
It was originally intended as Adrian quite rightly says, for making sure the towed unit wasnâ€™t lost, or tipped over whist in transit.
Here's a nice photo of it from Vinces Gallery
As you can see no post was fitted for an MG as standard