Thanks Leif!
I’m not too worried about overheating as I would have thought a water-cooled head would keep things reasonably in control. An aircooled engine may well be different though! The D21 plugs have a very long tapered electrode with a thin and pointed porcelain insulator so they “look” like a very soft plug. The AC87 “look” much more conventional and harder. I don’t know if that means anything though 🙂
Keith
