Hello Mr. Tore,
We had discussed the frames in Skizzenbuch with reference to the torpedo Tube loading hatch. However, we never touched on the subject of replacing a diesel engine and the disposition of the diesel room frames. The attached photo shows the upper frame missing while workers are in the diesel engine room. From this vantage point, it looks like these frames were cut into sections, but we never discussed the joining method for these frames.
Update: I found a photo on my U995 DVD that shows where the frames upper section in the diesel room overlap and are riveted together. See second image below...
Regards,
Don_
PS - I noticed that the ModelShipWorld.com (Where Katuna's photo was posted) used Skizzenbuch's colorized Plate 13 of the G. W. Diesel Engine drawing...