This is a bit odd, I was using the 4*60 to teach building and the nyrod or clear plastic rods in the red tube is what we often used. I now live in Vegas and fly from a dry lake bed or asphalt runway. It goes from the 20s to about 115 here so you could say we have a temperature shift and the plastic rods don't create that much of a trim change. I'm from Tacoma and now what Washington is like and if your trim is shifting more then a click or a beep or two you have another problem.
If the outer tube isn't glued in tight all along it's length about every 6 or 8 inches it will allow the rod to shift and it will change the trim but your temperature doesn't get hot enough to be a big problem.
You can change out the nylon rods and use metal without any RF problem. I have never had any type of RF hit with a glow engine, even with AM or FM. I did with gas powered planes but trhat was before 2.4.