As most Pietenpol builders find, the elevator control cables, forward of the bellcrank, have a bit of a cam action when worked through their entire range of travel. Many have no idea why this occurs… I think it is because of the slight change in geometry between the cable attach points on the control stick and their associated pulleys, as the distance from each changes slightly from low to high to low again. Anyhow, it is a common issue that poses no real problem, but the slack created needs to be dealt with in some manner. Most attach a spring to “pull” the slack when the cable becomes loose. I purchased a couple of screen door kits from Home Depot, for use in my tailwheel assembly (more on that later), and there was a screen door chain spring in each kit that appeared to be made for this application. Even the screen doo mount was perfect… so they are now Pietenpol parts, and doing a fine job.