I am very sorry you have been sick; I hope you get your strength back soon
Your work is gorgeous as always

I really love the new Type 31 ( there'll be a gray/black paint scheme too ?) and the water colors, but I have some dubts about the gun roster: are you sure you want use the 3.7 SF L/14.5 ?
I ask this, bacuse yes, one was used by UB-14 (I think, but not entierly sure hahah

), but the main small gun used by u-boats was this one

The 5cm SK L/40 Quick Firing Gun.
It was mainly a Torpedo-boat's gun, but it was also used as first surface weapon by many early subs until Nov 1915 [ Type 9, Type 13, Type 17 and some souces indicate even Type 19 (not to much sure about the last one)] and was used until summer 1916 by Type B2.
Type B-1 also used this gun: the first one to use it were the to boat sent by train to the Adriatic and used this gun until they were tranferred to Austria-Hungariy; the remaining boats (except of UB-2) were all fitted with this gun by the end of 1916.
I used the sound of that gun in the sound pack I sent to you.
Talking about sounds, have you recieved them ? Could be they be usefull for your work, or do you want I add something more ?

PS: one of them is not "good nominated" ( for "big Ammos Explosion", I meant the explosion of a munition ship, not the shell)