New path!
I snooped through grendagle's place and it looks like the furthest west she goes is ~700 (horse corral), so I'll jig around her place to center the path at 690, which is perfect because it lines up with an underwater valley I wanted to hit to cross the ocean. Speaking of, I think the ocean crossing should be on the seabed instead of underground to give the ride a little more visual fun. Especially with the new clear water texture in 1.9.
The seabed path hits the sheer chunk wall at 690/48/1020, which is where we'll turn to head towards Turtle. Whether that becomes pure tunnel or edges the chunk or what, I'll leave up to the miner(s).
The green dot could be a subway station that has a place up top (@250) and branches south (also where T's rail could tie in). The cyan dot is where the South Portal is located, and where we'd start our overhead paths.
I'll take care of the seabed path since I have some highlight ideas (and oodles of glass). Or heck, I'll take it from the Train Station since I know where to make the turns and take it to the sheer wall underwater. The tunnel builders can have at it from there.
Sound OK?
FYI: T's train tunnel is at y54. Not that we have to match that, but there it is.