I'm still not sure if it will even work, since I need to stack them to reach the underside.
If you stack thermal pads they aren't going to be very thermally conductive in series.
To build up the height you would need to use a copper or aluminium shim which is highly conductive and then add thermal pads between the two physical junctions (or better still use thermal grease on the join between the shim and the case). BUT having an electrically conductive surface close to the PCB is not a good idea especially as most thermal pads can easily be punctured.
As you are using fans, it is highly unlikely you need any additional cooling.
If more cooling is desired and the bottom half of the case is stone cold with the top half hot, I would consider putting thermal grease in-between any metal-to-metal contact between the two halves of the case and increase the height of the feet to give more airflow underneath.
If the airspace between the PCB and the bottom half of the case is not getting hot then the PCB can't be getting significantly hot. If the inside of the bottom half of the case is not matt black, just painting it matt black with the thinnest paint you can find (non-shiny marker pen?) will increase the absorption of radiated energy instead of it being reflected back to the PCB.
Statistics: Posted by pidd — Wed May 15, 2024 2:51 am