By chance I've progressed from the Naval Academy to this Single Mission historical scenario. Thanks for writing up your tips -

- I've been depth-charged and annihilated on my first two attempts because of firing torps on the destroyers as they first approach.

The stealth element is obviously what I sacrificed, so if I can bear to wait for destroyers heading out from Narvik I'll gladly set weapons for 2m depth and impact pistols. My notes on real actions of the time show a great number of Aal misses due to magnetic pistols misfiring. The confines of the fjord are a real contrast to open seas, so having this as a detailed single mission is excellent!