carbon fiber rod sounds good to me. The tube is supported in certain places along the fuselage don't know how much 4-40 rod I will have sticking out the end. Well scratch that idea. The tube goes straight back and does not come out the fuselage if it does I cant see or feel it. I used a nyrod in the tube to see how long it is. Guess I will put the servo where it is suppose to go. I will use carbon fiber tubes for the push rods Thanks Michael