I don't know nothin about nothin, but I have been using those dubro control horns quite a bit lately. Like Speed, I always use a dowel thru the control surface. Only thing is, on that elevator I would use a 1/2" hardwood dowel. Drill a 1/2" hole all the way thru the elevator then glue in a dowel. Then drill the dowel for your control horn. In my opinion, even if you put a plywood plate on the top and bottom of the cotrol surface, the balsa in the middle is still going to compress, which will eventually lead to a lose control horn

Pat