Must say that a Surcouf is an ambitious subject for a first sub. Here is a video I digitised and uploaded to Vimeo-
Apologies for the somewhat poor quality of picture, I did what I could with it to clean it up after conversion but the tape is third or forth generation VHS.
If you look at it from 12:21 onwards you can see Bernie Woods Surcouf. This is one of the original hulls the OTW kit is now based on, which I think was mastered by Maurice Rickett. OTW have retooled the boat, and added some extras that weren't supplied with the original kit.
Nick Burge made a set of firing guns, which you can see firing in the video (they fire blanks, BTW), and adapted the ballast system from a gas type to a recirculating compressed air system.
If you look at about 13 minutes you can see something poking out of the bottom of the boat- that's the main battery, a lead acid cell. I understand that was done to get the boat stable, perhaps to offset the weight of the metal gun up top.
Fortunately, this boat has survived, and is currently under restoration. It's undergone a complete refit, including a new hybrid ballast system using a vented tank blown clear with a diaphragm pump (a la snort), and a trimmed down Engel piston tank which will allow the operator to trim the boat for neutral buoyancy.