I am having issues with the Rectangular Wye connection where the offset for the branch outside radii is too long. In this particular example it is the 650mm dimension, which if constructed like this would adversely affect the airflow.
The outside radius of the Rectangular Wye is linked to its inside radius. A better solution might be to use the Rectangular Breech component instead. In this example the Wye is on the right and Breech on the left, with its values displayed.