RE: CH Ignition conversion on G26
Don't expect too low and reliable an idle plus with such a light prop until the engine has some more run time on it. That top end rpm of 6,400 is low for that engine / prop combo, and I suspect that your ignition timing and carb adjustments might need some fine tuning, or the tach used might be off. On a Zinger 16x8 prop max. rpm should be in 7,000 plus region running on the very restricted stock muffler.
Karol