Danny
There seem to be two holes for intake, was the left one routed to the back seat ? In that case, perhaps it was either/or, who got the warm air (and/or CO) and who froze (and it gets quite nippy in Canada).
ISTR that the pipe was routed inside along the starboard side to serve both seats with a simple butterfly flap by each footwell to regulate the warm airflow as required.
Southern hemisphere winters even in S. Rhodesia could be cold at night and with the airfield elevation of RAF Thornhill at 4,600ft a cross county navigation flight flown at 3,000ft AGL for example, meant the aircraft was in a chilly 7,000ft plus height band.