I've just received my order of speaker grill fabric, so I can now show you a bit more of the intended design:

The goal was always to have the top of the case covered in speaker fabric, but the challenge was how to achieve this without making the assembly too fiddly. The design idea was to use a kind of clamping ring to hold the fabric stretched and in place, which so far works really well. Here's an idea of how assembly goes:

I still want to add a neopixel-style LED ring to the design, and I'm waiting on this to arrive at which point I can do more fit checks and design revisions and then upload a set of STL files, as well as detailed assembly instructions. Stay tuned!