This one is a C&H. I looked for a RC Excel unit yesterday but I couldn't find one with 90 degree caps like my C&H has although when I pulled the cap off this C&H unit while it was running yesterday I was amazed at how strong the spark looked. I'm gonna take it out flying again today and we'll see if it continues to work.
This whole gap thing sure seems strange/unlikely to me. If It acts up again, I may have to buy a RC Excel unit and change the caps to 90's. Funny how the Rimfire plugs showed no signs of this and these RC Excel plugs did it every time (always only one - and I'm guessing it was the right cylinder, but at the time I didn't troubleshoot)