I drove as a passenger in somebodies sumo 2 weekends ago. It was about 14°C, so not exactly warm, but thanks to the heater we could drive topless (without a roof -

) and it wasn't cold at all... though windy

.
Clive if I understand you well you would - during summer - take air from for example under the car or so instead of from inside of the engine compartment, right ? Or from where would you take air then ?
I can imagine a more pleasant feeling during summer, than even warmer air coming in the cockpit.
Michael