Brendan
Yes I enjoyed the lovely symmetry too. I was familiar with the poem so didnt need to look it up. What threw me for ages was that I too had DHIRD to start the extra letters, and thought it was an author, until I eventually got the right one.
I love Gaston's themes and there is always accuracy, symmetry and elegance. They are not easy for me but I usually solve them. The 6Cs idea was brilliant.