I saw either an ad or an article about drilling three holes, but my reasoning was that to release trapped air one hole would be enough. I'm very happy now that the engine stays cool. When my wife and I first had the car on the road fifteen years ago, I would drive the car when temps were in the 30's and 40's, but those days are long gone, so 16 degrees is purely academic.

Next time I completely drain the system, I'm going to fill the block first through the thermostat hole, then fill the radiator. I didn't do that last time, trusting that the air would release when the thermostat opened. Live and learn.