Educate an old guy who never had anything that even hinted of needing 2x4's. With 3x2's or other multiples one carb runs the idle circuit, and the linkage is progressive, staging in the "secondary" carbs as you add more throttle. Do you set up 2x4's with a progressive linkage, so that it keeps the velocity up in one during idle and cruise, or are they both equally opened, both running idle circuits since the spacing might tend to overload one side of the engine a bit? I would imagine that trying to balance two sets of primaries to be right in the low to mid-range would be "interesting", as in potentially frustrating? Just wondering.....