Gato issues

Lack of diesel exhausts, no flood vents, superstructure aft end is wrong shape, no prop guards (note can be welded in place like early as builts or removable guard), guns suck to be blunt, main gun location varied so might need to build or remove sponson, aft torpedo loading hatch lacks hinge/spring detail. Nautilus had flood vent scribing guides and you can use them to locate the holes then remove the guide and cut through.