Are you sure about that Luke? I recall having seen pictures of Balaos with the navigation table clearly present, with a glass surface and illuminated below. Was that an after-war addition, when subs spent more time underwater?
See this:
http://www.maritime.org/tour/cr.php?pano=fl
Isn't the charts table what is next to the green table with a rounded porthole (I think that green table is the Gyrocompass)?
In any case, where was the assitant officer that made the plot on a maneuvering board based on the captain's range/bearing estimations as called by the guy who readed the scope bearing vernier/stadimeter? I think he was in the CT, but where?