No offense but from my experience that kind of thinking leads to nowhere ("it worked with his setup so it should work with mine"). Your dad probably got lucky that both the breathers he happened to use could flow enough that the crankcase didn't over-pressurize. When the PCV valve senses pressure it shuts and forces the crankcase gases out the breather side; with 2 breathers the engine has 2 big holes to vent out through at all times.
