[JAS]

In some hobby shops here there is a company that sells plastic 3/16" and 1/4" plastic 90 degree strips. I've taken the 1/4" 90 strips and glued it on end to the TE of the rudder top stp the wiggles (sanded a flat at the V and glued it to the TE of the rudder so it's a 45 degree drag on each side of the rudder).
I've see others that have taken the 3/16" 90's and glue on to each side of the TE of the rudder (like drawing). I usually glue it to within 2" of the top and bottom of the rudder. On my last one, with 3-9152's I didn't need anything, but my cables were really tight (plane is still flying with same servos, cable tightness and no wiggles).