Du-Bro make the best control horns I have found, they conform to the taper of the surface and come in two different sizes, they also have a long enough arm that it can be cut to whatever size is required to get the attachement over the hinge line without getting too close to the edge of the surface.

Mike

EDIT: Link to catalgue: http://www.dubro.com/hobby/ecatalog/dubro/00018.htm