<< I've notice that I can get the coolant temp. needle to drop
 about a needle's width by cranking the heat to FULL. The needle will drop
 even a little further if I turn both fans on full. Why is this? >>

The heater core is acting as additional capacity for the radiator or cooling
system. It is a "heat exchanger" as is the radiator.

I hope this answers your question.

Vic Montgomery