Carbon fiber and steel rudder cables, being electrically conductive, will absorb some radio signal. The trick with the antenna is to have it not be close to anything conductive, and not parallel, so that any blanking that does occur will only be at an angle across the antenna, not along its full length. A little blanking now and then as the conductive element and antenna move relative to each other with flight position and attitude will not be a problem. You do definitely need a tube of some sort to keep the antenna from flopping around inside the fuselage, and it should be probably close to the top of the turtleback, which would keep it a safe distance from pushrods & cables. An angled path for the antenna to get from radio compartment to top of turtleback interior is also not a problem.