A long time between posts here.I think I've run across the answer as to why that center area needs to be in those intakes but have no idea why this is. I'm mainly a Pontiac guy and have restored a number of the early 60s Pontiac dual quad setups for people over the years and recently repopped the linkage for the bathtub intake they made slightly over 40 of in '63. A friend, Mike Garblik, recently built a 46? Pontiac engine to install in a '62 Catalina and dynoed the engine while fine tuning a pair of 750 cfm AFBs installed on a repop of the old bathtub intake. The holes for the carbs on those bathtubs are open, like the ones on my cross ram. During the process of tuning the carbs Mike ran them on the open holes and with what the Pontiac crowd calls a "sheer plate", which is basically a spacer under the carbs that matches the bottom of the carb and extends the throttle bores a half inch or so. The engine performed better with the sheer plate than it with the carbs sitting on the open holes. Logically to me it makes no sense that it does but it does. The bathtub if for sure a single plane deal since it is a big rectangular opening that the runners branch off of. Any way this is my take on why cutting the centers out of a cross ram is not a good idea if one is seeking max performance. I just want a street/cruise in car so the intake will work fine as is for my use.