Unfortunately, the thread is a smaller size than the rest and the cupping was distorting the centre, even after much blocking and prying. So, I ended up cutting it off to save the middle, which I rather like.
Yes, I know, I could just lengthen the chains and so on, but I do not like spindly chains and anyway, I was getting a bit ...hmm... bored with the repetition!
So, moving right along...
solution is working admirably.