@Wobbles: So many people don't seem to realize how hard it is to get grabs with nana in the correct position to wobble in the first place
@knightpraetor: I'm not totally sure whether I understand what you are asking. If you are dropping float and then hitting bair, you are doing it wrong in any case (won't autocancel then). If you hit bair and release the float so quickly that you hit the ground within 6 frames frames, there won't be any hitbox because they first come out on frame 6.
Sorry, both are pretty obvious and you probably know them, but just in case that answers your question, or prompts you to rephrase it in a way that even some sleep-deprived German student will understand ...