i forgot about the china walls !
thanks for pointing that out !
now when/if a guy were to use a 1/4" thick [or whatever thickness is standard fair] valley cover, would there be a different amount needed to be removed ? and would this amount be dependent on the particular valley plate ?
i agree with whomever said to mock up parts that whose history is unknown. you never know what has been done, and if you don't, surprises you won't like may appear !