Its not clear to me why ayone would want to use a CDF because the other side does not know how to assess whether or not the other party will settle or not. Since they can't evaluate, traders will avoid it entirely. There is always a fear of losing your position + more. CDF's were only invented because there was no such thing as a stable asset. But now we have that because of cypto, athough I'm convinced the way bitshares is implementing it will not work. There is always a fear with putting up collateral, which is an obstruction to a frictionless transaction.
Not to derail your post, but I have figured out a way to create true stablecoin without needing ANY COLLATERAL. Its done using the LMSR structure that Augur and Bitcoin Hivemind are using for their Prediction Markets. The only difference is that its a TRUE non-settling prediction market (something Bytemaster could not deliver on when he first created Bitshares). Its effectively a LMSR that never ever has a maturity date and continues constantly.
I think this is a better idea than doing a CDF, and will help Bitshares in creating a true stablecoin, where both sides of the bet have symmetric risk profiles. You might be interested in this. Take a look. I think Bitshares should take advantage of this.
http://forum.truthcoin.info/index.php/topic,206.msg1075.html#msg1075