Gravity is what makes these things work, not friction, so I'd venture to say they are strictly kept at being level, and never used at an angle or as booms. That isn't to say something couldn't be designed that would work, but these aren't meant for that.
Why the devil wouldn't it have something like an integral cheesborough or gridlock type device to clamp down on the pipe?
Where is ETC around here to comment on their own product?