With my Y valve firmly floxed to the top outlet piece you can see I get unrestricted airflow in Pic 1.

Pic 2 and the task of joining the top piece. Many of these jobs I did on the same day. I’m using West System with the fast cure for many of these parts and just afterwards I make a crude box in front of my gas heater and run it full blast – good thing its winter here! Parts are sufficiently cured in a couple of hours to work on the next thing.

Pic 3 shows the bottom outlet fitting ready to be floxed in place.

Full flow outlet

Glassing the outlet in place

Bottom fitting