As you can see, everything fits (so far!) One problem I'm seeing is around the USB/Nunchuck ports, the edge actually has a gap due to the chamfer I put on the case - those two walls are 1mm thick due to tolerances, rather than 2mm everywhere else. I'll have to redo that.

Also, there is barely enough room for everything - the Sparkfun LiPo board will have to have the barrel jack removed, and all the pins on the LCD will need to be removed. The Teensy will fit on the back of the LED ring, and the ESP8266 is tiny, it'll fit almost anywhere.

I suspect I'll have to increase the depth of the case - it's 20mm right now, if I bump it to 25mm, that'll give me breathing room.