Just remember that pettit is a redneck pizza slinger. Take what he writes with a grain of salt. He writes so much and builds and tests so many airplanes he doesn't have time to think about what he says. C&H has in their instructions that you should not use a metal throttle rod. Why, I don't know. Maybe they are afraid it may bang against something. Others including people like P. Reviers are convinced a metal rod can be a problem. Theroretically, there is little chance of that. I have used a metal cable for years