Near as anyone can tell, the game does not have the functionality built-in for a dual-deck gun set-up to be selectable for the player. You can "see" the AA gun has the choice in the sim file, but the deck gun only has the one "player" position. Attempts to add a 2nd choice to the database results in two "trees" named the same, which is not a good condition for computers
- so "no", does not look like it can be done, short of altering the already baked cake. Which ever gun is the "default" for your boat is the one you can take control of, so put your best "gun" and "watchman" people on the other gun, and the so-so guys on the one you might take control of, unless of course, you never take control of the gun, then distribute your crew accordingly. The 20mm "deck gun" is treated like a deck gun though, and it will shoot at surface targets when within range. However, it does not do AA, since of course, it is set to "Deck Gun"... Which leaves me wondering why ships (including the AI subs) with dual-purpose 5" guns can shoot at planes with AA rounds, and the player's sub cannot?... but alas, the AI is what it is...
