Air ducting behind the dash

I have designed and a friend is printing for me some components for the air duct work that supplies hot air to the windscreen and cabin of the Land Rover.

This is actually going to be 3 parts glued together to reduce the complexity of the print.
The half size test pint

And then inside will split up the air flow unevenly so that the driver side has far more air flow than the passenger side.

The small top left aperture will feed the passenger side windscreen and the small lower right aperture the passenger foot well.