Ok, so if i get you right, its not the tip itself that is the "weak" link, its the unit where the wires connect to the main bulk of the sensor, the metal housing etc? This gets too hot and throws off the AF/readings? Therefore, the heatsink copper unit, to
1. take the tip out of direct exhaust heat flow, and
2. prevent the heat from wandering up the sensor housing and up into the wiring section?
all in all, mounting it far back as you say, is the best and easiest solution.
Ok, cool
Thanks man