A pointer to where they compute this in the paper would be helpful. There are a lot of comments to just read the paper because they calculate this or that, but I quickly read the thing through and either missed all these points being covered, or it's not actually considered.

"The Spaceline. By extending a line, anchored on the moon, to deep within Earth’s gravity well"

That's the concept. They could have fit that within in the title of the post.

Wouldn't be much use if it wasn't.