I would also test the hinges on the control surfaces, especially if they are CA hinges.

I bought a plane that had been hanging up and thought that I had checked it, an aileron fell off in flight, just so happened one of the really good pilots was flying it and he landed without incident, further inspection found the elevator was only being held on with two partially torn hinges.
I was lucky that I dodged that bullet and that plane is still flying three years later.