I'm in the happy postion of keeping a rock-solid low 80's although I'm not quite sure why. I have an 82C stat with a single 2mm hole, together with the race fan switch (73469). According to the archives that will make the fan kick in at 86C and stay on until the rad cools to 76C. In practise once the fan kicks in stays on pretty much on all the time. With the fan cutting in so early I'd expect water hitting the thermostat to be cold enough to close it but according to the temp gauge sensor in the water rail it's just about spot on. (for your survey purposes - 2007 EU3, supersport cams, standard 4:1 and inlet manifold, silicone hoses).