I have dealt with making pushrods for my 3d aircraft and have found that rods that are completly threaded are not as rigid as non threaded rods. The threading inside of a pushrod guid can also lead to binding if stray bits of contamination get stuck on the threads. My favorite solution is to cut down a pushrod that is threaded at on end and to solder a clevis on the cut end. It takes a few minutes longer then a z bend or 90 degree bend with a keeper but you do not have to enlarge the servo arm hole and connections have less play and wear better. threads you cut have a tendency to snap if not done absolutely right