I have two 5.1's and two 3.7's. The past four seasons I flew 1 o the 5.1 exclusively without radio problems with the exception of the telemetry. It would freeze after starting. I do plan to add shielding this winter and see what happens. Just one opinion here but I believe the two pickup ignition is far superior than the delay units in use today. I suspect this is due to initial cost, just like Mac and IBM, the best isn't always the most common.
I would believe that just adding the plug caps without the braid would solve my problem with telemetry but I did buy copper braiding from McMaster-Carr