No matter what turm/U-boat the controller is applied to, in
GunStationControllerPoperties there are four possible slot settings:
0 - SLOT_A01 (light Flak gun #1)
1 - SLOT_A02 (light Flak gun #2)
2 - SLOT_S01 (heavy Flak gun)
3 - SLOT_M01 (deck gun)
They are covering all the possible gun combinations for stock U-boats/cooning towers: max two single/double 20 mm Flaks, max one 37 mm Flak or one quad 20 mm gun, max one deckgun. The U-Flak is peculiar in having no deck gun and two heavy Flak guns instead of the one heavy Flak allowed in stock game.
Maybe we could rename the S02 gun bone/slot to M01, making the game to think it is a deckgun, but retaining Flak guns functionalities. If we do so, we should update UnitParts5VIIC41F.upc accordingly. If you are busy with other stuff, I can create a patch for you to test it in game. What do you think?