As I've been completing the Trantor level I had to adjust my meshes a bit. This caused lighting on my opening sequence to be reset. When I rebuilt it my map size went from 17MB to 166MB causing the load time at game start to exceed 30 seconds. That wasn't going to fly.
To fix the issue I reset the lighting on the opening level and only lit the select fly-by section:
Not an ideal situation but it doesn't look that bad. You fly forward through this so you only really notice your immediate surroundings: