Try the Odonnel!! It's better than OS plugs, and cheaper!
They last longer too, in my experience. Really, they're just good... To me, they give a non-turbo engine the stable feeling of a turbo engine, which no other plug ever did for me in my various SH-based (LRP, Mach, Dynamite, Losi, etc..) MT engines..
I haven't been running as often in the last couple years, but I have been amazed on the few occasions when I have fired them up, sometimes after 6-8 months of non-use, how they just fire right up and run great. Both my LRP 30 and 454.