That is really looking good, Hitman! I would love to add it to RFB if/when you guys complete it.
In regards to the shared texture issue, there is a very easy fix. Open up the SIM file for each sub interior (Gato_CT, Porpoise_CT, Salmon_CT, and Sclass_CR), and scroll down to the
RadarView section. You'll see a parameter called
Tga_file; this is what controls what graphic is used for each radar display. If you're really enterprising and want to expand this mod to the U-boats, you could finally rid them of the files they share with the American scopes.