i was looking at the thermistor datasheet again and noticed that they drop enough clues to work out what the beta/rz values are.
according to the datasheet, it is 10k Ohms at 25 degC, and 1990 Ohms at 70 degC. plugging this into the formulas on MeasuringThermistorBeta, gives beta 3671 and Rz 30857. then plugging this in to the calculator on ExtruderIO gives 0.014uF as the ideal capacitor (which is almost what we have at the moment, 0.01uF).
i haven't been able to test how it behaves with these "official" values yet.. i'm not in the same country as the extruder at the moment
pix.