Well, I just read your other thread, and it sounds like you're getting the same thing I'm getting. I'm %100 positive it's a mismatch between the bolt and the eyelet bushing. The only good thing(if there is such a thing) is that, as Rev.Chuck mentioned in your other thread, the play is only evident when the saddle(and thus the pivot joint) is unloaded. I ride mainly XC so I rarely notice it when I'm riding...it's only when I'm loading it onto the car that it bugs me. If your Big Hit gets a lot of air, I can see where the knocking might be a bit more evident.

Another clue for mine is that it's only a recent(just this season) issue. I've ridden the bike(bought new) for 2 seasons prior with no issues.