In my years messing with hot rods I noticed how some who were using dual quad carb intakes, specifically dual holley 4 barrel carbs with vacuum secondaries, used what you could call a vacuum balance tube connected to the caps of the vacuum diaphragms on both carbs to help insure the vacuum secondaries of both carbs were getting the same amount of vacuum thus helping to insure the secondaries of both carbs opened at the same rate.
My question is could this same thought process be used on the vacuum diaphragm caps/covers on my 71 CB350?
You possibly could do it like that but you would have to fabricate your own access ports to the carburetor vacuum chamber. It may not be worth the effort. These carbs are normally tuned by ear and sight.