Ive always used steel pipe,generally boiler stay tube,thicker wall and it wont crush easily,like ordinary boiler tube.Once pulled a boiler weighing 50 tons out of a building with 4" pipe,and a truck winch.....too many pipes will foul up the operation,they must be separated so they dont rub together and want to turn backward...Nowdays all the risk experts want you to do weeks of building demolition and giant,costly cranes to do what could have been done in a couple of days with a couple of laborers....This is why places like China and India are taking over...bet you cant find a single risk assesor ,or safety expert anywhere in Asia.They would starve.