I would also mention, BFX is no longer the only game in town when it comes to P2P margin lending. And the other sites doing it don't have any kind of FRR to manipulate the market. I've always been a huge fan of BFX's, but business is business, and if they don't do something to fix the broken system they have in place with FRR, I'm pretty sure at least some of my $ will be moving on soon.
Great to hear another exchange is getting into p2p lending. I just messaged OKCoin and they are charging 20% fees on earned interest. I asked for a justification for the high rate in comparison to Bitfinex, but they didn't offer anything.
Considering I think 15% is a little high already I may think twice about sending money over to OKcoin in the short term.
Peace