GetClientAimTarget gets the entity the player is looking at. It doesn't actually do what its name implies :O
I tried making the props spawn where the player looked, it did not turn out well when I tried it. I also saw potential for exploitation (spawning props to slow down enemies etc.).
And to answer your question anonpiss, I took a look at that script after you posted it and there's nothing in there that I can use to solve the bouncing problem (except changing the height at which the props spawn.
The Eventscripts versions spawn the props at the userid's location, but I try and replicate the same thing. It may just be a limitation of prop_physics_override.