RE: Excelleron 90 build in progress
I would suggest replacing the stock horns with heavy duty stuff such as Du-Bro. The horn on one of my ailerons failed in flight and the resulting flutter almost brought the plane down. The other aileron's horn was also beginning to fail, right at the screw's base where it meets the plastic.
Cheap insurance.
I replaced ALL the horns with Du-Bro the next day.
Art