Yeah... so for Tier 4, we've reached the core. However, there's an elevator going down at the core level. I was thinking that for Tier 4, we start going up on to the other side of Cradle. The skylark was shot out of space from there, so there's clearly something hostile on the other side of Cradle.
This isn't the most descriptive suggestion because if you read the title, it was a more of a note. So for those who keep putting a bunch of talk into Tier 4, describe more of going up instead of down. Reverse polarity... physics and such smarticle things.