When looking at the new side panels for the PiSound case suitable for a Pi4, you may be interested to know that the Pimoroni FanShim just fits OK below a PiSound board plugged into the Pi4. having used the Pi4 quite a bit now I think it would be highly advisable to include such a fan to keep the temperature down. The only modification I had to do was to remove one of the supporting pillars because it wouldn’t fit because of the shim. A lightly shorter pilllar might be beneficial for this.
The photo shows the corner in question. I put a nut on the bottom screw which just went through the hole on the fan shim, but a shorter pillar between the top of tehe case and the shim would be helpful.