gabe: out of curiosity, what was different in your tests? I'm guessing - heat dump because of different (lesser/bigger?) overclock and overvoltage? Different TIM used? BTW, have you tested different XT blocks for fluctuating performance? - I wonder if it's not possible that pin machining might slightly vary for different pieces of waterblocks, and it's possible that you're testing slightly better exemplar, while skinneelab might have recieved slightly worse (or slightly better HF exemplar). Also you double checked to use most restrictive p#1 with HF? Apart from that i'm out of ideas why results might differ except maybe you testing in only below 0.9gpm, where XT outperforms HF.