Off the top of my head, since he's not moving, his momentum is very different than doing the tricks on the ground. He probably had to get a feel for the difference (notably the difference in air resistance, again, since he's not moving forward).

My guess is the relative distance traveled is greater than usual for some of these things (train moves at a steady speed while he's in the air, while an equivalent ground jump he'd have a velocity that would be decelerating).