Rcexl only puts the resistor in the plug cap for the CM-6 spark plug. There is no positive connection that holds the high tension lead into the silicone boot. The full size plugs use a coiled spring that fits over the end of the plug, the other end of the coiled spring has two spikes that go through the high tension lead, when the cap is on the plug there is no way it can come apart. The picture is of a CM-6 type cap, you can see the resistor, it can be pulled out fairly easily, the clamp on the wire side of the cap holds everything tightlytogether. If you used the Rcexl ignition withtheplug cap for the 5/8 hex plug and substituted the NGK CMR6A plug for the CM-6, and removed the metal housing, you would have an ignition that would work on everthing but the 1/4-32 plugs.

Try this at your own risk, personaly I like the positive connection of the metal caps, I dont ever worry about my plug cap coming off. Also, although the CMR6A type plug is a resistor plug it also has about 1.5mm longer reach into the cylinder, don't know of any engines that would have a problem with that but there could be some out there.