I have a question that I am sure many of you know the answer to. When using a 6" main duct, I understand the recommendations for keeping the combination of sub-runs as close to the total square inches of the 6" area as possible. For example, many recommend a combination of a 5" and 3.5" run for the upper and lower collection points on a table saw that is connected to a 6" run. With the area of the 6" at approx. 28.3 sq. in. , the total of the 5" and 3.5" is approx. 29.2 sq. in. Since it is very difficult to size sub-runs to exactly match the 28.3 sq. in., is it better to choose a combination of sub-run duct sizes that total either slightly higher or slightly lower than the 28.3 sq. inches? Or, does it really matter at all in actual practice? Thanks for any help you can provide.