2nd AMD Card Disabled

I have managed to get hold of a Sapphire R9 290X 8GB to add to my basic mining setup which also has an ASUS HD 7950 and both seem to work well. I have previously tweaked the settings of the 7950 to their optimum and I am happy with the Hashrate. What I would like to do is the same to the new card as i think there is more potential in it. Although it shows up in the Radeon Overdrive software and I can see both cards, I am only able to access the settings for the 7950 and not the R9 290X.
Does anyone have any idea why this may be?
Thanks in advance,