If I have a good place to hunt, I figure the best way to shoot. Then I go home and reproduce that position as well as possible so that I can practice shooting in the manner that is best while hunting, and at the distances I would expect at that location.
Shoot from your knees, or from a sitting position. It doesn't matter.
But, my opinion is that trying to go from sitting to crouching is not so good because the muscles are too tense to shoot in that position consistantly. At any rate, if this is what your blind will allow, then practice. And, if you can't hit in practice, create a different set-up.
The key is to adapt to your environment and not the other way around.