I think what you're seeing here is the same bug I reported:
The problem isn't just at zero. ST charts actually draw a border around the sides and bottom as if it's going to fill it, even when it's not supposed to. Especially look at message #4 in that thread.
Mitchell did you run this against st2.1rc2?
Asking for another repro is pointless if you haven't. This is just drop in code into the kitchen sink.
Heath - Did you check to see if this is the same bug as the one I linked to? It seems so to me. At least that one is marked as OPEN.
It could be the same but claiming no repro when it clearly is against st 2.1rc2 is rubbish.
raised in premium support to get a little more attention.