We used Siller Bros. Skycranes one job we had six 18,000 lb units going on top for Mission Foods flashing caps were attached to the curbs where the units rested , the rotor wash created a low pressure area on the roof causing the flashings to lift off and roll up into burittos and flung off the roof, So a worker piled steel beams around the next curb to keep it from blowing off the roof, I made sure no one was down wind side of that pick, The skycrane came back with another unit and that loaded buritto rolled up with a filling of beams and sailed off the roof it made a hell of a dent in the parking lot. In Mexico we did a Bose plant and I got to ride in the lift seat back home, Fun times.