Perhaps because I'm a great fan of telling and of having the freedom for fanfiction, I think my own answer to your dilemma would be to perhaps write a companion piece that goes into the behind-the-scenes information that you know. It'd be canon, it'd be there, but it wouldn't be right there in the text as Word of God to keep the fanfiction freedom from happening.

Does that even make sense? My brain may be a bit fried from my own Nano push today.