It would be better to fire two channels on the ignitor from one output of the ignition expander and keep it simple. You would just need two more 3 channel ignitors. Verify with motec but this should work. I know you can fire two Denso 580's (they have a built in ignitor) from one output.
Here are some pictures of how the Beru 997 COP's fit: Please note these are fully seated in the opening and on the plug.
Bottom Fitment: I did not have plugs installed but this is what it looks like pushed all the way in until it hits the valve cover.
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