Oops, my mistake. If the RCS uses a 10mm plug (NGK CM6), then it's not a resistor plug. I bet there is a resistor in the plug cap between the high tension lead and the coil that contacts the spark plug. The ZDZ uses a Falkon ignition with Brisk plug or the replacement (NGK BPMR6F). Both are resistor plugs. A resistor plug is needed because the electronic timing circuit in the ignition may not work properly with a standard plug (according to the instructions that come with the ignition). Resistor plugs are pretty cheap (about $2.20).

For the BME, I think they have the small plug option, which uses the NGK CM6. The Extreme 110 shows this plug. Not sure if it uses a shielded ignition. Check with Keith Baker.