It will be good to see your design once you get it finished.
Peter
Peter, yours was posted today, hopefully with you tomorrow or Friday.
Attached are pictures of your black case with my PAW bits fitted as well as a version with mounting lugs. I sent you a different lid however as I wasn't happy with the finish of the one pictured below.
Note, you need to spring the case walls apart a little when fitting the Pi/bridge in order to clear the audio socket, while you slide it towards the P3I antenna socket hole.
The case lid is held on with the 4 screws into the Pi mounting pillars, and a block / latch at the fan end - so it needs to slide into place. Carefully check the fan wires aren't pinching on anything.
Let me know how you get on with it and any suggested improvements.