The sub-roadbed for the return loop under the Enterprise branch is complete now, and I'm working on the branch itself. And I've got the pics to prove it! :-)
Notice the 'access pit' in this photo; since this is too far to reach from the aisle, I've built an area to stand it for working on the branch itself. I don't intend to cover this, but rather have the scenery high enough around it to hide it, while leaving it open. Or at least that's the plan.