Couldn't humans crouch under them or otherwise easily circumvent them (throwing nades under them, shooting under them, etc) easily defeating them purpose of building a barricade?
True. However, if we decide to build them on the ceiling, we are deciding that we dont need them to hinder human movement, but rather to cover a ceiling structure from damage. On some maps, this would be a real lifesaver. edit: on a further stretch, I think it would be good if their shape changed depending on if they're on the ceiling. I'm seeing a broad, flat leaf shape, much like a beaver tai that curves in toward whatever its protecting.