Insane,
You can get the Rimfire plug from C&H Ignitions. It comes with the ignition system for the Saito. I'm still using the original plug although I bought a spare JIC when I started using gas.
I put several hours on my Saito as a gasser. Plenty of time to wreck it if it was going to happen. I'm flying it now as a glow engine. It has never run better.
I came up with the 16:1 gas
il mix thru Email conversations with a guy from the south who has converted many 4-cycle glow engines to gas. This guy and a bunch of his pals were using gas in OS and Saito 4-strokes. Do a search of the RC Universe and RC FAQ archives and you'll find him, I think.
If you want a light weight small gasser, How about the FPE 2.4 with C&H ifnition. They reportedly don't come any lighter. There's one for sale in the gas engines forum.
Cheers,
CR