Six pack response...

I don't know how relevant this may be to your question, but years back Chrysler Power magazine there was an article on tuning six pack secondaries by changing the vacuum bleed size on the secondary vacuum actuators to control the opening rates. The factory carb bleed orifice size differed according to the application, this article showed drilling and tapping the orifices for socket head machine set screws and drilling the set screws for custom orifice size. The general idea was to open the secondaries as quickly as possible without making the engine bog under load.