Wow, thanks for helping guys.
RDD- I think you are right, it was probably an old topic that I found by accident, but I'm not positive. On the other hand, do old topics cycle out, or should it still be there even if it was really old?
OohFeeshy- You are exactly right! Excellent drawing! A "lip" is a great way to characterize it. Did you post in that thread, or just read it? Perhaps we could find it that way if you posted.
Boboboy- Not the same tank I'm looking for, but that is quite awesome. I'll read through that post when I have some time though, as I think the discussion is probably similar.
As for searching, I too have searched on just about every term, including "how does it work" and variations. Despite that, I hadn't even run across the threads Boboboy posted!
-P