For me there would be alot bigger weight penalty than that. I am only running the old style YS stainless header pipe. It only weighs 1 OZ. My engine weighs 35 oz bolted to it's lightened aluminum mount. There would be allmost 10 OZ plus the ignition battery and switch harness.
Why did you not like the APC 18-8W, was the spool up very slow (heavy). What rpm did it turn it? I reweighed my plane last night, and it is 9lb 11 oz.