Just wanted to share my opinion about the new Flirc case for the RPi4.
Conclusion: The Flirc case works great for passive cooling, it looks very nice and it is cheaper than most solutions(probably the cheapest).
RPi4 2GB version and the room temp is about 24'C.
....Sysbench test....
temp=49.0'C
temp=58.0'C
temp=60.0'C
temp=62.0'C
temp=60.0'C
temp=62.0'C
temp=64.0'C
temp=65.0'C