Superclamp (and Superclamp style knockoffs) are generally useful for anything that is not too big for the jaw extension - i.e. most theatre seat "hardware" (handle, part of the mount etc), drink rails, some balcony constructions etc.
BUT ... I often find that to get a good solid lock on whatever it is I am clamping to, I need to take out the little rubber wedge, and/or by the time I get the superclamp good and solidly locked down, the post is either tilted or just not at all where I want it to be.
Dave Bishop gave me this accessory and all I can say is this thing is the greatest since sliced bread, rapid adapters, shock mounts, T-bars. Put this little gem together with a superclamp and you are set for almost anything you will encounter in a clamp/extension pole scenario. It is not a lot of bank, well built, allows you to correct for ANY angle you end up having to contend with, and I now consider it as essential to my gear bag as mics, cables, recorder, and batteries.
I never leave home without it and use it at almost every show I do now!
http://www.bhphotovideo.com/c/product/656152-REG/Impact_9101880_Umbrella_Bracket_with_Adjustable.html