What would you say is a safe voltage for the GDDR2 on these chips with plenty of airflow over the chips? I've tried the stock 2.05, 2.1, 2.2. Not sure if I can safely push 2.3-2.5v, I've got the Samsung ICs and they clock like garbage, 832MHz is barely stable but I think my PWM needs beefing up as it's stable with the core under 700MHz.