RE: spark plug question. (resistor or not)
The Falkon ignitions for ZDZ are fully shielded, but the instructions also insist on the use of a resistor plug. They advise that a non-resistor plug may interfere with the electronic circuit of the ignition.
The 3W and DA ignitions are also fully shielded, and they include a resistor in the plug cap and a compact CM6 non-resistor plug.