There is a cheat, a modified map file, that let u create your own map. So u could have removed collusion's, shoot true walls, and create a glass floor for example high in the sky where u can shoot true and kill anyone without moving. But im not shure if its there yet. If it would the creator probably wont publish it anyway.
And why u fall to the ground, i dont know. Have u tryed other maps? Maybe it has something to do with the X-Y changes thats coded in the trainer.