No Rival, ever, has been or will be as overstable as a Champion Teebird, much less a Brinster Teebird. It's a great disc but I don't know why people keep bringing it up in this thread.
Obviously you've never thrown a first run Icon Rival. Flat as a board, and just as, if not more, OS than a Champ Teebird. I get zero turn out of mine, and a healthy fade. It's basically a lower speed C-PD.