The small end A should be completely open.

Pole Plate End

1. The most desirable fabrication is to have the end completely left open.
2. For acceptable alternatives, the half-circles, slots, and round holes must equal 30% of the area of the internal diameter of the pole end of the tapered arm for 3" (8 cm) and larger internal diameters. The opening must equal 45% of the area of the pole end of the tapered arm if the internal diameter is less than 3" (8 cm).