There is a clamp that is better suited to the "Y" piece for the GS exhaust system where it meets the single pipe off to the muffler.
This type comes off a Morris & instead of the original 2 piece design, this is a 4 piece one & makes a silent seal effortlessly. They are quite expensive though $40 - $50 each.
With this one taken care of, you now only have 4 more to look after which can be a full time job if the car sits around a lot!
Actually the others still really require at least a smear of good quality exhaust bog, then - bang, tighten, bang, tighten....