ORIGINAL: Pull Up Now!
I never said don't use that Dubro hardware. I'm saying that if you use it in the way I described, you're exposed to elevator degradation. Also, let me address the hardwood mounting underlayment. If one is using wood screws to hold a control horn to the surface, hardwood should be present (or soak with CA, as AA5 said). But many control horns come with both the horn, AND a backing plate. These work fine with balsa underneath, but I'd sure limit that to small/medium sized planes. HOWEVER, I think it's important to point out that with the Dubro #913, using hardwood underneath won't keep that pivoting from happening as I described, especially if the control surface's thru hole is a little oversize. Many people wouldn't size the thru hole all that carefully. So there will be some slop in the hole, resulting in enough clearance to allow that slippage. Sure, a tight fit hole in hardwood would be better, and would limit the screw's side play, but I think people would have to be aware of this issue beforehand. Otherwise, it wouldn't occur to people to size the hole so tight.
Any time you use a screw type of control horn it MUST be run through some type of hardwood! We have been using 10-32 screws for control horns on 40% IMAC aircraft for years. The difference is that they are run through a 3/4" birch dowel that gets installed in the surface. Usually a foam surface and the dowel is in contact with the upper skin, lower skin and leading edge material. The screw horn is threaded into the dowl and epoxied in place. For a 50cc airplane with flat balsa surfaces on would want to use a horn with at least one square inch of mounting surface. Classic case of the wrong thing was being used. IMO the hinge came apart first ( The pin NEEDS to be sunk into the surface material after the 90 degree bend ) the resulting flutter was a contributor to the horn failure. The horn failure will happen again due to the lack of surface area spreding the load and being installed through balsa.