An album with all stunt zones: https://imgur.com/a/caNR6l8 (They aren't "landing" zones, rather 2nd 3D trigger you have to fly through. Your vehicle has to be not flipped or tilted too much while first entering it. A stunt jump can end prematurely if you touch any walls or even peds/objects). If you want a better look in-game, you can use Simple Native Trainer + https://www.speedrun.com/gtaiv/resources/jfdg8