Mateo, I am not picking your engine apart or anything but I am curious as to why you went with the "CM-6 type" plug. You stated that you guys were using brand name parts on your engine, why not set yourself apart from the others and put a real CM-6 plug on the engine to start with and save everyone the trouble of having to replace it.
Even DLE won't put a real plug on their engines, I don't get it. Is NGK banned in China or something?