There seems to be more to the Pure X2 technology of the Pioneer4you and YiHi mods than I initially thought. With a TCR of 0.000875 (=TCR of SS317 which is slightly less than SS316L) the relative resistance change is 0.0875% per degree C. No problem so far, but if the coil resistance @ room temperature is as low as 0.067 Ohm, the absolute resistance change is 0.0586 mOhm per degree C (= TC accuracy) I don't think the DNA200 (and other TC mods) can do true TC on coils with such a low TC accuracy (yet). Like with a SS316L coil of 0.064 Ohm (same TC accuracy), once the temperature setpoint is reached on this coil, TC will behave very erratic.