Why do I open my big mouth and set myself up to fail? 
It’s only been a day since I wrote that with regard to my “modular box” in the beam, and as it happens I spent a bit of fretting time in the middle of the night sorting out what I think I’m going to do with it.
It’s probably best just to finish it and do a show and tell - but I’ve just tweaked all the little modules slightly in finer detail as well as the end pieces so that it will be easy to adapt for any width I think. I can’t get around my own design criteria which will make it a lot more fiddly to build than simply screwing on a box.
I’m having a think about a similar box at the other end too, to house a panel mount socket for the router, and to allow hidden routing of the Right hand side cabling through a conduit (a shiny chromed one of course). The power supply will be mounted on the conduit exposed (shudder) and I think that will leave me with an inch or two of cabling that you’ll be able to see if you peer through the slots in the tops of the braces! 
On another note - while trying to talk myself out of Painting the orange top covers silver as per my original intent, I noticed that the light on the Core produces exactly the two toned effect I had envisioned in that sketch above, which is pretty cool. The silver is not quite the right colour, but it’s closer than the orange so it will have to do.
