The big issue with an unbalanced count is pretty much just that. The key count is pretty much when you first see a marked advantage according to the KO theory, but remember that that advantage is less when you are deeper into the shoe (and more if it comes early). In my opinion though, you just have to trust the system you are using and stick to the plan...unless you use some detailed math to adjust the key count as the shoe gets played out (of course, that defeats the purpose of the unbalanced count in my eyes).
As far as having a "big bet" out at the KC, I would suggest learning the preferred KO method...it uses a step betting system with the count, and you won't have a big bet out there at the KC--just a more graduated bet.
Oh yeah, and because the casino cuts off about 1.5 decks in a 6 deck shoe, there is no guarantee that anything "must come out".
good luck
