The eagle has landed. 6'6" with a XXXL over a XXXL heavy flannel. I can zip it up okay with the flannel and it doesn't seem too large when I go with just a tee underneath either.
Shoulders are a touch wide and the upper sleeves seem big. But I'm not really sure I could size down and still be able to wear it with a flannel underneath, which is what I'm most likely to do