In reply to David Coley:
i girth hitch to the tie in points
i also have that loop at the end -- the purpose i see out of it seems to be to make sure the prussik does now slide through when no it use. i dont see any real negatives that would come from not having it -- i could be wrong.
i have seen purcells tied with 2 pieces of cord with 2 prussics that allowed for a lot of adjustability -- looked like a faff to me