I've had friends try them out on Biner brakes and it works but it's a bit goofy. If you look at the internal shape the Doval aren't true ovals, but ovalized D's. (they get slightly narrower towards the spine so it's not completely symmetrical) They end up adding friction to the rappel settup (like it needs any more). I haven't heard anything about it but I would also watch the rope running over the wire gates on rappel. That would make me nervous as hell. Probably best to go with the Mountie standard. Either that or borrow a few for a month and call it good.