By the way John I'll never forget the first thing I read that got me thinking about this, the first thing I mean in an American whiskey context (since vatting/blending in Scotland is very old).
I can't recall now where I saw it, but it had to do with a distillery worker talking about a batch of bourbon. He said, if it is not right or not strong enough in taste (something like that) we just add a barrel of rye to it. (He wasn't talking about labeling and I am sure it was labeled properly under whatever law applied at the time, I am just trying to make a general point). And that was like a eureka moment, hey why can't I do that!
Gary