Depeche,

Comparatively speaking, the weight of the pushrods is nothing compared to the weight of the servo.
Add to that the fact that moving the weight of a servo to the rear of an inherantly tail-heavy plane is not simple linear translation from a CG perspective. Since there is a greater moment arm (weight * distance) on the rear servo than there is available for the offsetting counterweight ahead of the CG, it will take much more weight in the nose of the plane to compensate. Thus increasing the overall weight considerably more than necessary.

e.g. 4 oz. located on the CG balances and weighs 4 oz.

4 oz. moved 4" back from the CG must be compensated by 4 oz. 4" ahead of the CG to balance and now weighs 8 oz.
4 oz.* 4in. (16 oz.-in.) == 4 oz.* 4in. (16 oz.-in.)
OR
4 oz. moved 4" back from the CG must be compensated by 8 oz. 2" ahead of the CG to balance and now weighs 12 oz.
8 oz.* 2in. (16 oz.-in.) == 4 oz.* 4in. (16 oz.-in.)