Steve if you buy the coated cable like what is sold as a pull-pull system it will operate in the plastic tube the same as a flex rod. It would take many a year to wear into the plastic tube. I use the car antennas as a plastic tube, usually around a buck for about a 12" piece. I use a small but somewhat strong spring between the servo arm and the cable end. The cable works just as well as a rod or at least I have had no issues to date. Good luck.