I do not know what type of u-boat model you would like to build , you did not say type 7 or type 9 etc. If you have a model of the type 9 you can name her "U-848 "as this boat still had it's main deck gun but also had the enlarged upper gun platform with the two twin 20 mm guns and a platform with a single quad 20 mm gun. It looks like from the pictures that the guns still have the flak shields installed.
As time went on most boats took off their gun flak shields as it made the boat very top heavy which made the boat roll more, also this created more drag underwater decreasing underwater top speed. They did foldup but this encreased the setup time when needed and even when folded still caused some extra drag.
Most deck guns were removed after mid 1943 as they were seldom used due to strong allied defenses, such as air cover , hunter killer groups and since most ships were now sailing in convoys there was little if any chance to use this gun.
Most U-boats that still had their deck gun was the boats used up in Norway against the Artic convoys to Russia.