I have zero experience with dual carbs of any kind on a stovebolt engine, but the concept of a bigger secondary venturi makes sense. It's what GM did to an extreme level with the Quadrajet. That carb uses two very small primary barrels with 3-stack venturis for excellent low speed performance, and two huge rear barrels with a spring loaded air valve to provide virtually unlimited airflow with the right fuel mixture at full throttle.

Bigger jets have very little to do with high speed performance. It takes a bigger venturi and/or throttle plate to flow more air, then the jets are selected to mix the correct amount of fuel with the extra air.
Jerry

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