The heater has 2 outlets and the car uses 4 vents. 2 for the screen and 2 for the footwells.
I had to make up 2 splitters, so I used some bathroom waste pipe,
Cut 2 45 deg so that it divides the air equally
Air in from the top bit should split evenly.
and glued them together.
Painted them, but they will never bee seen.