there is two thing i will some times do
have you ever went to a building that you can jump off of and spawn a car, put in the flying car code, drive it off the building. Then fly it as high as it would go jump out and use the parachute when you need to.
After doing that a few times I know now that you can land in the water and not get killed (with out the parachute)
OR
have you ever tried doing stunts with any kind of vehicle using packages. For instance you put in the infinite ammo code and you throw all of the packages as far as you can in one spot drive the the car's backend over it run away and press the button. it should do a front flip.
you can make a car do a 360 if you load up the right back and the front left it should turn.
You can also stick all you can to the back of the vehicle and blast it forward.
or do the same as my top paragraph, but this time park the car so the packages are in the middle. then it goes sky high!