I would not use 2-56 steel rods full length from servo to control surface. The length is such that unless you are supporting the golden rod sheath every few inches, flex would cause you all sorts of problems with control. If you supported the golden rod every few inches, what's is that cost in weight? Also the steel rod this longis heavy in its own right.

If you decide to do this anyway, do it the best way possible. Useshort segments of the"INNER" rod ascentering guidesfor the steel rod; it also helps reduce friction between the steel and the outer sheath. Keep in mind that this set-up won't tolerate bends well. Bends will cause lots of friction and you would have a problem driving the control surfaces accurately. To install the outer sheath accurately, first put a carbon tube inside, about 1/8" in diameter for a straight and true run.Then add the supports to the sheath. Once the glue sets, remove the carbon tube and run the supported steel rod. It should be nice a smooth.

But if you go through all that trouble, forget the steel rod and just run an .075" carbon rod instead. You can ca or epoxy standard brass or steel threaded couplers on the ends of the carbon rod. It is far lighter push rod method than steel rods

If the original dowels don't appeal, then you might consider using 3/16" to 1/4" carbon tubing. It would be lighter and stiffer than wood dowels