If the LiPoly pack was almost full, then the current would drop. In order to maintain a charge rate of 1.2 Amps, you would need to apply a much higher voltage than the cells can withstand. To oversimplify, electricity only flows from higher voltage to lower voltage. The greater the difference between the source and destination voltages, the higher the current flow between them.

When the pack is completely empty, the charger will charge at the full charge rate of 1.2 Amps. As the pack nears 4.2 Volts per cell, the current naturally decreases because the voltage difference decreases.

The best way to discharge a LiPoly is by putting it in an airplane, and flying it!