Actually, I don't think Wozza's right there. A long time ago I successfully adjusted the point at which G effect occurs on a specific model. It's a setting in either the aircraft.cfg or more likely the old .AIR file. I'll go take a look and see if I can find the setting. I recall at the time the model I was playing around with was a fighter where the pilot wears one of those high G tolerance suits (maybe F18G or F22?), thus the need to change the setting.
BTW he is correct that the G onset is set pretty much right for a civilian sim - a sustained 3-4G would black out an untrained individual, which I can personally attest to, flying as "ballast" in a twin seater aerobatic glider.
LPXO
~Edit: got it, I think. G effect might be linked to the airframe G limit which is a setting in the .AIR . That said, I might be wrong, too. The app I've used to open Daisuke Yamamoto's F18 .AIR is a later version of AIRED (from flightsim.com) than the one I used to use. I could have sworn there were four G limit settings, not two as you see in the pic. Two controlled the +/- airframe stress limits and the other two controlled the onset of black out/red out effects. But in this version of Aired everythings changed. Maybe the G effect is elsewhere... I'd suggest downloading the app, make a backup of your .AIR file and explore it. Just FYI, the .AIR is where M$ used to store all the aircraft performance and spec data way back when before they invented the .aircraft file. In current models the order of priority is 1. any XML gauges, 2. The .aircraft file, but 3. anything not specified in the aforementioned is still retained in the .AIR file...
LPXO