Convert to HBD. This contract is similar to above, but in reverse and with a 5% fee. If a user executes this contract with 100 Hive, after 3.5 days they will get 95 Hive worth of Hive Dollars. The exchange rate again is determined by the price feed in the same way as above.

Not quite right. The HBD is delivered immediately. The converter needs to post HIVE in excess of the current value, and after 3.5 days the excess (based on future feed exchange rate) is returned.

I personally preferred it the way you described it but it ended up being implemented the other way because of a preference for faster supply response to the potential of big price pumps.