Thanks for the compliment, Z!
Apparently, Geirr's book is not yet out in Norwegian, ironically, NimitzFan. I look forward to reading it in English, since my Norwegian has been eclipsed by that of my 2 yr old son, Rohan the Red ... fierce and famous little Viking.
I have visited the naval museum in Horten. The director there didn't have information about whether Gyller had 4 tubes in whatever configuration in 1940. I e-mailed him from the States before I came over and after my visit to the museum ... and no reply. He's involved with the model magazine over here too. You'd think he'd be interested in any angle to popularize (Norwegian) naval history.
Last spring, Rohan and I took the Drobak ferry out to Oscarsborg Fortress and saw the Krupp guns that crippled brand spanking new Bluecher (which then was taken down by the reservist torpedo battery crew) and smashed Luetzow, critically delaying the German occupation of Oslo, which enabled the King, Parliament, and GOLD to escape.
The Germans knew about the guns, of course, but not the "secret" torpedo battery. Their research only went back to the start of WW1, and the battery was built in 1912 and ammoed with Jules Verne looking Whitehead torpedoes of Austro-Hungarian manufacture! ... which worked splendidly thanks to years of loving care by their reservist crews, between family picnics, of course.
The island is now a national park very popular with families, and it has an excellent museum with many models and a 1:1250 model diorama. There are beaches, picnic areas, and food shops and a restaurant.
I've got a photo of Rohan chucking a rock at one of the guns which happily didn't fire back. I'll try to find and post it.
Something I have been told was that all of Norway's ports were smothered in fog on 9 April 1940, with the exception of two of them - Oslo being one. That is why Norwegian coast defenses did so poorly. In Trondheim, they fired at the sounds in the fog ... and missed (battle cruisers Scharnhorst and Gneisenau, I think).
Remember that the British were planning on invading Norway too, but the Germans beat them to it. LOTS of interesting encounters, not the least of which being Warspite's escapade up Narvik Fjord.