MjTheGamer :
Finstar :
You're just gonna have to test it and see how far it goes. And don't worry, it won't break if you go too far (your mobo likely can't even feed enough power to fry it). It'll just crash and restart the driver/your pc.
Ok. is 100-200 MHz ok or less
I can't give you numbers since (as mentioned above) every card is different. Your just gonna have to see how far it goes.
I'd dial in around +50MHz and then go up by 10MHz increments until it's unstable and then bring it down until it's stable under load for a while.