WHOA. How did you do that? Just fire in the air?
Well, I fired from the beggining with the turret aiming backward while accelarating, to get a good speed for the jump (works almost like nitro but in Rhino style!). When I start falling down the mountain, I have to rotate the turret about 45º and keep firing, and pray for the tank to hit some good ricochet spots.
Oh, and I had to do it all in cinematic camera view. The other camera modes don't allow you to rotate the turret properly (the turret moves automatically with the camera).
It still took me a lot of tries to do it right.