I use a ply plate mounted flush with the surface. I then attach the MK offset control horns. They attach with 3 tiny #2 size wood screws. The screws come with the horns. They work great and are adjustable for height. Also these horns put the pivot point over the hinge line.

I use the MKD0815 these are the medium aluminum horns. They also make a small horn too. In other situations I have used the MK large aluminum horns and converted the Offset horns to make them the large size.

Works well.

I use these for ailerons, elevator and rudder.

A dremel router bit set to the depth of the plywood plate, I choose about 1/8th inch plates, will remove the balsa tot he proper depth. I then use Pro-Bond polyurethane glue and clamp the surface to a flat table. This keeps the plate flush with the balsa skin. Sand it and fill with model magic around the edges of the ply plate and once covered you can't see the the plates. To install the horns I drill the hole equivalent to a #2-56 drill for tapping. I then run the wood screws in, remove them and use foam safe CA on the holes to stiffen the wood.

Once its covered and ready to install the horn I use some thick CA in the hole and run the screw in. Have not had one vibrate out, no plates come loose, and the setup is clean and simple. Also it saves me lots of time in setting up the bolt thru control horns. Another advantage is the horn load is now spread over a wide area. Another great thing is the tops of the control surfaces are clean and have nothing sticking out.

Not the cheapest solution but I think the time saved and the finished result is worth the extra $25 you spend on the model. Others will disagree but to me its worth ever dime I spend on it.