**Ok I have taken the cave into Deep Paint 3D and painted out the floor seam.  Then I dipped it into UV Mapper Pro and welded the crack in the ceiling.  Now I am back on the lighting.  Here the min shadow bias is cranked to ten on each of two lights inside the main cavern area.

I am trying to figure out how to make this a prop so my camera access panels will show up and  then I can try and figure out how to open them up to make the inside visible from the outside.  Having to keep the camera in the cave limits the shots available somewhat.
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Free men do not ask permission to bear arms!!