I spoke with Klaus of LSE about this plug thingy, and he said he did research on this with instrumented plugs around 1989 which resulted in recommending Automotive plugs with the right heatrange in place of the Aircraft plugs he recommended up to then. He specifically protested the use of the Champion 386 plugs sold by another vendor  in an article in Sport Aviation about that time. He says that a plug in the proper heat range will have two shades of tan on the insulator with the darker side near the electrode. if it is no change, the heat range is too hot or too cold. Cracked insulators on a plug is a sign of detonation not temperature. He reminded me that those planes racing at Reno with LSE ignition and recommended automotive plugs have never had a cylinder go bad, but several planes with aircraft plugs and Magnetos have. He also said that those fellows running full-out at 250 mph TAS or more on the 1.5 hr race to Oshkosh at 2000'  have 2" MAP boost and are running at or above 100% power the whole way! To his knowledge none of those racing who have LSE EI have had a problem with detonation or pre-ignition. However, there is always a way to over- advance the timing, regardless of the ignition device used.