First off, he probably uses the speed boost feature on the runup, cos on every stunt u can clearly see he's not using the dipping method until he's close to the bump object. Second of all, he uses 3 vehicles for all his stunts, I mean COME ON, you might aswell spawn a goddamn ramp in the middle of the road.
I am also certain that he uses the 'always godmode' feature (it's a steedmod in IV integrated into the simple native trainer) and I wouldn't be surprised if he "fixed" the handlings if you know what I mean.