Many kits are made to precise standards, and this includes the pushrods. They are perfect for the recommend servos, but when using servos that have the output arms in a different location, those included pushrods may not work as well. This happened to me, and it meant that I needed to make up my own pushrods for the elevators. I purchased some 2-56 threaded pushrod from the local hobby shop and cut it to the size needed, which was only about 3 to 4 inches long.
But I found out that threaded rod is not very rigid and tended to flex a little when the control surfaces were at full deflection. I had some copper tubing lying around that would allow the threaded rod to fit inside it. I cut some tubing so just about 1/2 inch of rod extended out of each side. I then used 2-56 nuts on each end and tightened down the tubing to the rod. This created a very rigid pushrod that was also very light and clean looking. You can save even more weight by using aluminum or carbon-fiber tubing instead of copper. Of course, I just used what was in the shop.
The nice thing about this is that you can make custom-length pushrod any time and not spend a lot of money doing it. Now I have extra 2-56 and 4-40 threaded rod along with the matching copper and aluminum tubing in my shop—just in case I need another custom-size pushrod.