I still dont see how this will make a negative G. You aren't creating any lift upwards that will force the helicopter down you are just letting the helicopter drop when you push the nose down, even after a climb. Am I wrong? I've had a few "rollercoaster" rides in a helicopters myself although I havent done any myself yet and I know the feeling your talking about like your stomach is trying to escape but its the same feeling you get jumping off a diving board its just freefall.