Hmm, never heard of copper push rods. As far as the nose heavy condition, try moving servos like you said as well as the battery. The battery will help plenty. In most cases you can balance an airplane just like this. Push rod flex is a big problem for a lot of aircraft, so many are going to a pull pull setup. This is a more complex way to go but it does save weight and there i virtually no slop in the cntrols. Another type of pushrod is the carbon fiber type. These are extremely light weight and and stiff. As far as the rudder servo goes, I think it is just having trouble centering. Check to make sure that the rudder isn't hard to move or their isn't excessive ca in between the rudder and fin. If the airplane is sitting on the tailwheel, try lifting the tail up and see if it stops. If that doesn't fix it then you may need to look into the servo. Hope this helps