Keep ground in view mode will keep the horizon in the view even if the aircraft is going off the screen. Try using a different zoom mode and using the black switch on the controller to get a glimpse of the ground.
Realflight is only made for Air vehicles. You are better off getting a driving sim.
If you would rather use Realflight I will try making one, but I am not too good at modeling.;)
P.S. is it okay if I post it for version 6.5? I don't have G5 or G4.