I don't know about the editable format--the whole "beauty" and
strength of this letter is that it will have a live Red Hatter behind
it, and that the customs folks will be able to get in touch with this
person if they have questions.
If we would have this letter editable, we could not guarantee that it
would always be edited and used properly. Even though I have no doubt
about the good intentions of the people on this list, I would not
trust that much to the rest of the world, who all could easily
download the letter off of our wiki.