Keep in mind, that an electrical faillure of the HT lead OUTSIDE the ignition box, CAN cause severe interference, especially if the faillure is not immediately killing the engine. So make sure you have your failsafe set such that it kills the engine at the minimum, and neurtalized rudders if possible. This will allow regaining of control to bring in the plane in a deadstick. Because if the lead or cap are arcing outside but the engine keeps running, the plane is toast...