[XXi]

Well.... in most cases it comes like this:

3 watchmen ( sometimes 2, depends on the seamen assignment ),
3 sonarmen ( two in the compartmen, the other one resting... if possible ->4 )
2-3 Torpedomen - usually I solve this out giving right specialization to 2 Officers
1 Medic
3 Repair ( depends on the situation, with the progress of war I strive for optimum of 2 Officers and AT LEAST 3 Mates, saved me quite few times )
4 Machinists, if possible. Plus AT LEAST one officer with the specialization.

Flak Gunners, Gunners - not more than 1 for each. SOmetimes I stop just givin specialty to an Officer.

Notices apart: I tend to have one Officer Flak-Gunner-Watchman
The other: Torepdo-Watchman ( plus, for example, repair )
Helmsman-Torpedo-Machinist
Helmsman-Watchman-Machinist
the other usually machinist, repair, medic or something like that....

PLUS: don`t forget that using some mods affects the final outcome as it changes the rate of effectivness. See Tonnage Mod for example. Or Hollywood Mod....