Simon.
On KNM Kaura (U995), KNM Kya (U926) and KNM Kinn (U1202) they removed the wintergarten completely before they were put into norwegian service 1951-1952 and made a new different one as can be seen below. The structure was completely welded, no hatches or doors, the railing protruding about 30 cm out from the topfloor widening the circumference of the floor by having 3 floorbars. The structure tapered considerably down to the casingdeck as can be seen on the photo.
Tore