You mentioned that your leads were 18" from your ignition which is fine. Is your throttle pushrod non-metallic? I'm guessing it is.
The ailerons shouldn't be a long enough run to cause problems. They are usually the shortest. The antenna is a good start. What are your engine on and engine off range test differences?
Twisted leads often help to keeep the noise down, and your leads are all one piece and at least 22awg correct?