One of the few things the Silent Hunter series hasn't managed to deliver yet, is a fully modelled sub interior. SH4 actually provided fewer interior spaces than its predecessor. While lazy sods like me were content to grumble about this in reviews and leave it at that, two industrious CAD craftsmen - subsim.com forumites Mikhayl and Tomi - have been busy making the missing compartments themselves. Tomi's breathtaking engine room isn't complete yet, but, even in its current state, stands head and shoulders above anything produced by Ubisoft Romania. Truly amazing work.
Another subsim.com regular has come up with a different solution to the missing interiors problem. Spanish(?) Kapitan 'Johann Vilthomsen' is in the process of U-boatifying a room in his apartment. From the photos I'd say he's on the right track but definitely needs more bunches of bananas, and puddles of sweat, diesel oil and pee.