I'm using the same JR Aluminum horn I've been using for years. It has two set screws as well as the standard top load screw to hold it in. I put it on as centered as I could but had to adjust the trim to like -12 or -15. Then I set the end points and was just fine. 65 on one end and 82 on the other if I recall correctly. I'm definitely getting full throw. Got the rub on the arms to prove it.