Obviously, this is an iterative process.  I revised my drawings of the axis tensioner for the Y axis a few times before trying to print it.  When I created the screenshot for it I noticed that some of the notches didn’t line up properly.  In any case, the part that fits around the pulley’s axle came out well while the part that fits on the Y stage edge didn’t come out very well, was fragile, and snapped when I was cleaning it up.  I’ll edit the file to thicken the wall of the Y axis edge piece and try it again.