I believe those that have the oem airbox could mount the relocated CDI on top of the airbox. Maybe secure it to one of the 'Y' top tube frame rails.
Now there is a hollow in the 'V' formed by the top tube plates welded to the frame. Have to remove the tank to see it if memory serves me. That too might be a spot.
As an alternative to a private endeavor manufacturing an extension cable/harness, I wonder what the time invested would be to get a recall done by Triumph corporate requiring them to fashion a relocation kit similar in scope to that of the rear brake reservoir kit they made up way back when.
