Are you talking about something like this beast?
I'm not sure there is anything like that in the game, but maybe there is. Would they mount where the 37mm are now? Do you know the time period when the guns would have been on the vessel? keltos01 has been rather busy with work lately, but he'll be along sometime and reply. I'm not sure what you're seeing with the "sea-through" portion, but are you certain you have all of the texture files where they're needed? Are you running it in Stock SH4? I'll have to load my copy up and see what I see...