Gentlemen,
Since this question is also one I am following, I did some looking around.
I found this.
I think that it shows that the control links to both the FWD and AFT Dive Planes for manual control are similar, based on the known link running through the aft head.
The mechanism for each dive station is mirrored, and it looks like similar links are running off towards each end of the boat, on the starboard side.
One arrow is a little close to a valve - I am not pointing to the valve, but to the link behind it.
I do have a possible path for the FWD link, but it is supposition.
Based on the deck height differences between the FWD Torp room, Officers Quarters, and Zentralle, and the supposition that glands and universal joints if run through the fresh water tank would/could contaminate the water with grease - could it be possible that the fwd link might have been run below the Officer's Compartment Decking, through the battery room, magazine, and up into the steering station from there?
That path would avoid the trim and torpedo compensating tank 3, and it would avoid having to go through the fresh water tanks, sound, and radio rooms, as well as would avoid Tore's bunk. :-) It would also have most of the linkage accessible for maintenance.
Just thoughts.
I still need to fiqure out how it links to the FWD dive plane control below the torpedo tubes. You can see that area from my cut-away part of the model.
Christopher