I confess that I still haven't finished this, despite several days of occasional progress. I'm missing most of the "middle top". I've got 4dn (of course!), but the only other ones I have are 17dn, 25dn and 16 ac (and I'm not convinced I have the latter two right).
Would it be possible for anyone to give my some subtle hints? (possibly on another thread, so as not to pollute this one?)