I am installing my Selkirk chimney- when I put my chimney pipe adapter onto my first length of class A pipe, I twisted it into place and put a locking banc over the joint - I asumed a locking band was needed but there is not room in the celing support recess for the adapter/chimney pipe with the locking banc in place - any body know if this joint needs screws or something else instead of the locking band?