[Lord of Angmar]

I see what you are saying, doug. I try not to use Tolkien's letters to prove or illustrate a point about Middle-earth unless there is no text from the Legendarium itself readily available to directly support the point. However, the letters can be regarded as 'canon', I suppose, inasmuch as whatever Tolkien clearly states in his letters will generally hold true to his intent. If we should choose to disregard the assertions he makes in his letters as non-canonical to the world of Middle-earth, we would be, to an extent, voluntarily ignoring certain truths present in his writing. It would be different if the letters were not published (as perhaps they should not have been, since they do reveal a lot of the 'bones' that Tolkien meant to keep earthed), but since they have been, it is safe to say that their assertions and revelations about Middle-earth can be taken as canon.