Bill's suggestion is best if you want to conserve energy.
by using 1 ohm, you are driving 600mA or so, through the 7805 with input to output differential of 7V.
obviously the device gets HOT.
why not try 2 ohms/ 2 watt so that the current through the device would be around 300 to 350mA, balance taken over by the series pass transistor? it helps to cool down the 7805. however , when you try to mount the TIP2955 on the same heat-sink and close to 7805, it conducts the heat into the regulator.
So, place it either far away or use another heat-sink to suite the needs.
the 10 ohms could be at least 1/2 watt