Copying this over to HaD to enter the 2017 contest. The main build log has thus far been over here:

https://sites.google.com/site/dbtayl/blog

Regarding how I've thought through the design ("Design Your Concept"), a lot of work has already gone into this. I've got 3D CAD files for the PCBs, so those should all fit in the case. I've verified this via 3D printing a test. The rest is also designed in 3D CAD, so it should fit. Most pieces have already been machined and fitted at least once.

There are two real challenges are making the darn thing, and getting the hinges right.

The former is mostly done, actually, thanks to the CNC mill I built. It's taken FOREVER, but the pieces seem to mostly fit together.

The hinges are the real challenge- I didn't have a 3D CAD model to start with, so they're drawn in as best I can measure. Right now it looks like I was slightly off in those measurements, so there's a small gap in between the lid and the keyboard when closed. I intend to see if I can hand-fit it to make it work and, barring that, re-machine the lid to fix the issues.

I guess one other point of consideration is cooling. Fortunately the CPU draws something like 3.5W fully loaded (4 cores + GPU), so passive cooling will suffice. I've already done stress-testing using just a heatpipe (no heat sink), and it stayed plenty cool. That should improve further when the heatpipe is connected to the case- the entire chassis will act as a heatsink for the machine.