I listened to a former secret service member talk on the radio as he outlined ways their security protection totally messed up coverage. Two things in particular: When he was in the service they would have either rotated the stage to block a path from the metal building roofs, and/or parked a big tractor trailer truck and trailer bed in the path with something on top of it, like a flag or whatever, to obscure the view to the stage; and/or they would have positioned people (possibly local law enforcement) at those metal buildings with specific instructions that do not require decision making, for example "no one goes up on the roof, period", and similar instructions.