Lawrence, I suggest you consider what was written
in message #101717 as a solution.
Petr, I didn't use thermal paste, even though it's in the drawer.
Heat dissipation can certainly be better using the paste.
If you want to put paste between the FETs and the heatsink, you have to unscrew several screws,
not just the one holding the pcb. That's why I didn't do this.--
Gyula HA3HZ