If I'm feeling lazy, I don't even bother trying to gain access to the room to destroy the device. When I have a clear shot into the large room below the device, I... kinda cheat. With a PWT, enter coordinates that will aim the PWT projectile underneath the approximate area of the synomium deivce, then angle the PWT upwards into to floor. Let it fly and wha-la, head back to the access points. Of course, then you don't get to reap the benefits of captured tech, but it makes for a quick mission.