this would require a second price feed for hbd

The internal market price can be used as a second price feed, but it isn't all that great because unless my market maker bot is running (which it wasn't until a month or so ago), the spread can be enormous, making the price quite ambiguous. It is also a small enough market that it could easily be manipulated, although the same sort of 3.5 day window would help prevent that.

I agree this isn't a good way to go.