First, send the ignition system to Terry. It's probably the cap. There are few who can take care of your ignition problems as well as he can.

With regard to the distance thing. I set just about all my gassers up pretty close to the same. First, I don't re-use extensions from another plane. Same with switches. I sell the used stuff to the glow fuel junkies when I'm done with them.

The flight battery and the ignition battery will often end up within two inches of each other in 30% and under planes. When that happens it means they are within 3 to 6 inches of the engine and ignition module. The ignition switch will usually be within 6" of the batteries. Both switches. The receiver has been known to reside within 8 inches of everything else.

I also always use a metal rod with ball joints on both ends for the throttle rod. The only plastic on the rod is what holds the balls in the fixture. None of the servo leads and extensions are ever twisted, but they are always good ones. I always use a shielded cap.

Guess what, no glitches with a ppm receiver. Range check distances are rarely less than 200 feet, antenna collapsed. I would think that distance would be eliminated from the interference equation after all that.

Personal opinion is that ignition/engine interference is usually caused by sloppy workmanship, inattention, or lack of knowledge. Sometimes all of the three. Using the wrong type of part for the job often ends up the culprit, too. Other times it will be caused by someone trying to go cheap in an expensive arena. Take the time to do it right the first time. If the cost is getting too high, fly something else while you build up a little capital rather than shortcut the project. Think it through and look for areas where a loose connection or metal rattle could pop up. If you locate something that seems like it could, it will, so correct it before it happens.

I would much rather see a plane on the bench for a little bit longer than as a pile of broken dreams on the ground.

If all the above sounded harsh, please forgive if you will. It wasn't meant to be, just unfettered.