volfy
I think you'll like this one, I tried to install to control horns after installing the pieces of wood on ailerons. however the screws will not go through the leading edge. It's too thick.
I got frustrated so I called Great Planes trying to find out why didn't send the control horns with the plane or why there is no piece of wood on the other side.
the person who answered doesn't know why they don't have control horns. He doesn't know what piece of wood I'm talking about. However he found a note (on his computer I guess) that says backplate is not needed just put screws from the front side. They don't need to be supported with a black plate.
I will probably go and purchase longer screws to use the backplate. I'm not comfortable using the control horns without backplate. I'll make it work somehow.
I'm not very brave at this stage to modify the plane like you did I do have enough experience to do that. It is my first one in ten years.
Again, thanks for your input and hopefully I will e-mail you when it is completed (and tested).

Happy flying