Replying to The Double Back

So one of my friends seems convinced that he can do a double backflip. He just learned backflips last season, and is set on doing one this year. I think he will die. The momentum and skill it takes(which he really wont have either) is alot. It seems to me like our jumps, in ohio i might add, are only about 20ft or so, and you need ALOT of air to get anywhere close. He keeps telling me that its only a mental thing, and that it is a one-motion type flip that he can do....i dont know want him to die, any help? At least it would be a good video...