[CapnScurvy]

In Optical Targeting Correction I added the Radio Room to all American subs (TMO 2.5 has it for the Gato interior..... which is also the same modeled interior for the Balao). You can get to it through a Keyboard key click; mousing the Radio Room door when in the Command Room; or simply move through the door to the Radio Room when in the Command Room free camera. The Radio Room comes from SHIII. I made small changes to the room to distinguish them from each sub.

I've messed around with adding additional rooms too but there is a drawback......the more rooms you add, the greater memory usage is required to model them. It could be most computer's today can handle the extra load on memory, its just that the game balks in giving you more memory access over 2 gigs (the SH4 game just wasn't designed for more memory access). SH5 does allow for additional memory access, which gave the developers the idea to have almost the complete sub interior modeled. The only problem in bringing the SH5 modeled interiors to SH4 is the format the models use.....their completely different than the SHIII or SH4 models.

As Dread Knot pointed out, the developers didn't add any rooms to the American subs outside of the Command Room (the same design was used for a couple of the different subs), Conning Tower (not one for the S-Class), or the outside Bridge.