Measure the horn and get an arm that matches the distance spread between the holes. I use a Du-Bro HD arm ([link=http://www.shopatron.com/products/productdetail/part_number=670/101.0.1.1]HD arms[/link]) and 4-40 pull-pull cable system ([link=http://www.shopatron.com/products/productdetail/part_number=518/101.0.1.1]Cable system[/link]), parallel and it stays tight. Make sure the horn holes are inline with the rudder hinge line.