It was pretty cold inside the car this morning, so I don't think the monovalve experiment worked. Could be the inner workings of the monovalve or just the fact that it was about zero degrees outside. The engine never got past 60 degrees centigrade, so I will next try blocking off part of the radiator. I don't think it is the thermostat because the car stayed right at 80 degrees until the cold snap hit. I am also going to spend a bit more time trying to get the flap to the floor vent to stay open.