Important stuffs to consider when OCing;

1. Consider the room temp.. dont just go for the best OC that people from countries with snow can do... we have a very hot climate... the card is already fed with higher than most temp in our country...
2. Watercooling is much better when OCing.. better heat removal... make sure watercool setup allow cold water to the heatsink on gpu.. not heated water from cpu heatsink... try putting radiator in between...
3. Not all chips acts the same... some extra overclocked gpus are hand picked for better durability and higher clock... same wafer does not mean same potential...
4. Good power supply... make sure enough Amps on the 12v rails... sometime can fail during loads...
5. Pray to god more... lols ...

Anyhow, i gotta say you're pretty brave to OC it.. i'm too scared haha... maybe after i got more backup money i will try mine... and thats a pretty respectable oc too...