I have a span of 60". I want to put a tube of hitch stock, 2" x 2" x .250"(?) across it, attach an electric hoist and lift maximum 100# several times to bring my welder up on the roof of the containers during construction. Would that be safe? What would be the actual maximum I could lift with this? I don't want to lift maximum, just like to know how close I am to the bending point to allow for safety.