The game has a fully working crossfire profile and it works wonderfully well. However the game developers changed the exe.name at the last minute, so it stopped it from working. I've raised it with our driver guys and it will be corrected in a future driver update, so please accept my apologies for that.
Fear not though, i was on it immediately and have a perfect temporay solution. It's possible to get crossfire working with 99% scaling easily, just copy my custom crossfire profile and enjoy 99% scaling flawless crossfire performance.