Tower is looking good Bianco.
I too have solved the Deck etch problem by using Styrene 0.13mm over the top to centre the UZO.
In regards to the Wooden slats to stop the crew sticking to the Tower in cold weather.
In all the photos I have and the videos U552 I cant see to any ( or not many) Slats on the sides in the early version.
there are photos showing a few on the Antenna housing
Only when it shows photos with a Wind deflector ie later war, does lots of Slats seem common on the side walls.
Have you got references showing these slates?
PS Also the Eduard Tower set provides the strange box with a hole, the needed hatches and seats etc that is missing with RCsubs.
BUMP and 3rd photo shows no Slats and also no Box with a Hole?
?
So my conclusion is that the Box with the Hole is some sort of temporary apparatus?
cheers