Well, to be honest, i've no desire to play guessing games as to what the problem is, between personal file adjustments and any extra mods run over the top, sky's the limit on what the problem is, and i've always said that i'm absolved of any responsiblity once that occurs.
At any rate, I remember how i structured how deck guns are made available, and the way i did it, it is impossible to get anything but aft mount for tambor and gar. So unless theirs a typo on my part (which i doubt, otherwise id have had more people screaming at me instead of a few compliments on how nice that larger 5/51 is), id have to say, completely uninstall all mods, and re enable just TMO without any personal tweaks or mods and see if the problem still occurs on a new boat. (once data is written to save file it ignores whats in the data directory)