Well, I did manage a spiralling negative G turn and held it for about a minute at starting altitude of 20k and the G-meter showed about -3 the whole time. However, I thought G-effects were cumulative. Not once, did I get a hint of grey, black, or red out UNTIL I passed -3.0 G on the meter then It was complete and not gradual. I also managed an engine cutoff in the process. IIRC, Falcon 4 modelled both Black and Red outs, but perhaps they weren't modelled correctly. And of course you were flying much faster, so I suppose you would notice them that much quicker.