I've managed to complete the upper level baseboards, lay all of the track and install the wiring ahead of schedule. Granted, a lot of the track is not yet fixed to the boards (look at some of those dog-legs!) and some of the wires are swinging loose beneath the layout, but I'm pleased with progress so far.
You can see about half of the temporary return loop in this photo, the freight headed by three SD45s will swing to the right, crossing the precarious chipboard bridge (more supports required) high above the fiddle-yard before making it's way to the other side of the loft. Eventually it will reappear from the right at the far end and head back toward the camera, but on the left-hand track. The line dead ahead of the train is a long siding for off-layout storage.
The same train is seen from the opposite direction, approaching the point at which it will take the diverging route rather than continue ahead into the siding. The grey box to the right of the picture is the Lenz LK100 reversing loop module, balanced there for ease of access while I was testing the wiring.
The layout is an end-to-end design, but with return loops at either end any train left to it's own devices will eventually end up back where it started if nothing is in it's way. Once I obtain the required track-circuit modules, this upper level loop will effectively become a linear fiddle-yard, enabling through traffic to be more convincingly portrayed. But for the last couple of hours I've sat back with a glass of wine and just watched a couple of trains circling the loft, something I've not been able to do before. I was suprised to find that a train moving at a typical freight speed will take 20 minutes to return to it's starting point in the fiddle-yard. Nice!
Currently On My Stereo: Black Sabbath - Paranoid