Johnnysplits, Snuts here:
I was posting in relation to the general question presented by the original poster.
You have a very spacific installation (with no details). Which receiver are you using? I imagine your ignition wire to your plug is factory shielded (again no details).

I do fly Giant scale planes (nothing bigger than 100cc yet). I too install rf conductive pushrods, servo's within 3 inches of motor, and ignition module. Never have had any rf problems. I do seperate my magneto type ignition systems from my flight electronics. This is carried over from my gassers, early 1990's and FM (later PCM) radios.

I may edit my earlier post:
In resurch, I learned Spektrum offered marine spacific receivers to overcome potential of rf problems due to skip on water surface.

THIS IS NOT INTENDED TO BECOME A BRAND WAR!

Again I hope this may help.

-Snuts-