The part that gets hot on both of my bitx radios (40 and micro) is the power supply chip on arduino board. it gets too hot to touch. The PA only get slightly warm after an hour long phone qso.?
I had thin sheet of aluminum that bolted to the power regulator and it is markedly cooler.?
I have not set my radios up for digital?
Run radios both at 13.8v regulated.
_Dave_ AD0B