TTB - Nearly every design project is torn between strength and weight, from an engineers viewpoint. In many cases, weight saving is crucial, and round section often provides adequate strength - whereas the strength gain from box section is often badly offset by the weight gain. Cost also comes into the equation, with round section often considerably cheaper.
bugdevheli - I presume the sprag clutch engineering calculations didn't include adequate shock load factor? Nasty stuff, that shock loading. Did you know that a load suspended on a crane hook, if suddenly dropped 2", will almost double the load on the hook/cable/boom/jib? Yes, I must confess, I like the old feet, inches and ft lb stuff. I must be as old as you, I certainly have nearly the same amount of white hair ...
