I would not block the tranfer areas between each side. I've never found any advantage anyplace doing this, and when I tested spacers a few years ago, the 4 hole spacer provided the worst results everyplace.
It woln't hurt anything to let one side of the dual plane intake see the other side, and there may actually be a few benefits from allowing this to happen, much like adding an "H" or "X" pipe in the exhaust system ahead of the mufflers. In the intake manifold specifically, the air to each cylinder stops for an instant when the intake valve closes, much like getting a door slammed in your face. This puts little shock waves into the incoming air stream. It may help distribution, and airflow to allow one side to see the other to minimize their negative effects. I'm not sure about all this, but I do know it has an effect on power output, and may effect efficiency and fuel economy as well?
The dyno and dragstrip testing we did a few years ago with intakes/spacers showed more power and quicker ET with more MPH with a small cut-out between the secondaries. We saw benefits as well with a semi-open spacer, solid across the front and open between the large secondaries. This testing further supports letting one side see the other side.
Another thing not to do is remove the entire divider on dual plane intakes between both sides. Right on the dyno we saw a BIG drop in mid-range power and torque doing this, with only a couple of additional HP at really high rpm's benefit. Maybe too much of a good thing?
In any case, it's all about application, and the total combination of parts, etc. Keep us posted on the testing, and the results. You will find that the APT system in the carburetor will allow you to have full control of the A/F ratio at light load/part throttle. With the triple venturi area in the carburetors primaries, the fuel milage will be considerably better than any Holley or Holley "clone" once you nail down the best setting(s)......Cliff