The other option is to install a voltage dropping resistor in series with the input to the 5 vdc 7805 regulator as well as adding the heat sink (with thermal compound). I added 2 - 2 ohm 2 watt resistors in series (4 ohms 4 watts total). That dropped the heat of the regulator significantly. I then tested a 5 ohm 10 watt resistor on the 5vdc output side while running the rig. There was a slight drop in voltage, less than .2 volts, and no impact to the the rig performance. The regulator will get very hot with 1+ amp, though not into thermal overload. My estimated total current draw was 1.15 amps for this test.
Still, the best solution is to run separate regulators, as that way you have less dependency on input voltage. With the voltage dropping resistor, under heavy load, the input voltage needs to be above 11 volts into the rig. This drops as the 5 volt current drops. The regulator needs at least 7 volts in to perform correctly, All this is in the 7805 data sheet.
Above is my experience. YMMV