Receiver Whip Antennas
It would scare the heck out of me, too, Kris! Black magic, yes?
I'm an antenna engineer, so my knowledge of interference is somewhat limited, however.....
If the problem surfaced after you changed from the larger wire to the smaller wire, I'd sure look close at that. Interference is generated by the collapsing field of the apparatus and one should be able to hear it on a traditional AM radio. You don't need anything fancy.
I'd wrap a mini AM radio in tin foil, stick a 8-12" piece of # 12-14 wire between the radio and the foil and "sniff" the wires (run it about). You'll hear the interference. Guaranteed. If it's continuous without nulls, just shorten the 8" wire, maybe to 1-2".
You will see graphically where the problem is (please be CAREFUL!).
Wire size, routing, spacing, the use of ferrite beads(!), grounding(!), will all make a difference. You will hear it.
Interference isn't generally a 5 minute fix. Might take hours.
But how many hours did you spend on that beautiful plane?
Please let us know your findings. Maybe there's a 'plan B'.
Good luck, my friend.