Man, the top mesh won't hurt airflow. I have an ex240 up top, with the fans mounted on top of the case between the mesh. My yate loons flow air just fine in a pull configuration (pulling air from the case, through the rad, and out the top).
I will tell you this, though... The ex240 will not fit up there without cutting away a significant portion of the plastic, and I see no reason the butcher the too panel when it fits perfectly inside.
"One man can change the world with a bullet in the right place."
"Life can never seem so real as when it faces extinction"
-U.S Marine Corporal Ron Szpond, Vietnam - 1966