The back plate is rattling because it is not tall and wide enough to fit the grooves in the top and bottom parts of the case. I don't know if it is on purpose because of the case moulding variations / orangepi+daughter board placement variations or who knows why. I personally installed passive dual side heatsink and made a custom back side metal grill so the hot air can escape. If you need any help regarding modeling or making custom parts, let me know. CAD/CAM is what I do. I would consider helping you design what you need for free.

Sounds interesting. What does your A600GS custom back plate look like?

That's a great idea, I might do the same.

If you mean the weights idea here is one cheap and easy solution. Go to hardware store and buy two galvanised steel perforated plates 80x40x2mm. Two of them give perfect weight increase to A600GS, they fit in the middle of the bottom part of the case and they won't rust. Then isolate them with electrical tape or put some isolator between the bottom of the daughter board and those plates. The plates are easily fixed to the bottom of the case with a glue gun and can be easily removed without any damage. 15 minutes of work

Good luck

I think the case is "ok" ... I did some rework with tape to prevent the metal plates from rumbling around and hold the audio jack in place ...

I already started to design a case with integrated 3,5" Floppy drive but it´s far from complete 

I think A600GS case is very well designed, very well molded, quality plastic etc. I would not change it I just made some modifications and I installed two 2mm insulated metal plates to act as weights underneath the daughter board and now is very stable on the desk and cable movement does not move the device anymore.
 

The back plate is rattling because it is not tall and wide enough to fit the grooves in the top and bottom parts of the case. I don't know if it is on purpose because of the case moulding variations / orangepi+daughter board placement variations or who knows why. I personally installed passive dual side heatsink and made a custom back side metal grill so the hot air can escape. If you need any help regarding modeling or making custom parts, let me know. CAD/CAM is what I do. I would consider helping you design what you need for free.

Sorry for the problems described by the previous speaker, yes indeed the early versions had a electrical bug and the firmware had it's child illnesses, but that has changed.

I got my ZZ9000 from a production batch last year with latest firmware 1.13. and for me it was a true easy plug'n'play experience. Installed the card, P96, Genesis on my A4000T and all works in less than halfe an hour. RTG inclusive native put through and automatic flickerxing like a charm, 256MB autoconfig RAM expansion, Ethernet not the fastest but ok for Amiga needs and much faster than with a dialup modem. The only problem which still exists is the USB port, couldn't get any memory stick to work, at least not automounting partitions.

Can't tell about the Sound expansion, as I don't have it.

For me it was the best deal for my old A4000T, solved 3 problems out of the box for me:
1. Native put through and flickerfixing, finally could retire my CRT
2. Lack of RAM, 256MB is a nice addition
3. LAN connection, modem retired

About, the problem described updating the firmware by the previous speaker:
Upating is done very easy by copying the new BOOT.bin to the SD card, NEVER EVER TRY TO DO THIS ON A WINDOWS SYSTEM, as Windows screws up the file, it obviously doesn't like when you copy a file named "BOOT.bin" into the root of any drive. So best to download and copy the new firmware updates on a Linux system.