I had my doubts about that under board transfer pad for the bottom of the board under the processor now that i have one on all 3 of my boards it does work!
I think the bottom metal plate needs cooling fins on it though. Not really large deep ones but it needs something better then just being a flat plate.
I thought the Edge would benefit from it the most, but that 311D gets pretty warm itself
That pad is recommended thumbs up icon
Yes, the heat produced radiates all directions, and hence needs cooling on all sides
also combined with the thin PCB makes it more heat conductive through the bottom as well 
Khadas had plans to modernize new radiators, I don’t know how much they are moving in this direction now
@BowerR64 The new radiator and cooling scheme are in progress as planned, please wait patiently
Will you any new technologies in the new cooling scheme, heatpipes, Vapor chamber ?
it would really be “cool” if you used them 