Hi Siara, thanks for the help but no, the vent in the picture is for the Stern main buoyancy tanks between frame numbers -1 and -2, the Stern Driving Tank is between frame numbers -10 and -11. This missing vent should be approximately 2.5 m from the end of the stern.
After looking at all my plans again I am starting to think that the Stern Driving Tank was only found on the early U-boats like U-570. By about mid war they have removed the Stern Driving Tank and just made the Stern main buoyancy tanks larger.
In the plans I have for the original form of the Type VII, VIIB and the very early VIIC, the Stern main buoyancy tanks are smaller than the later VIIC. I also see that some of the plans for the late war VIIC/41 have