We have both opening windows quarter lights and rear windows on the 356, but found the flow of air onto the driver was minimal. We had therefore resorted to a 3" hole in the Perspex with a bit of "donkey dick" running through it pointed at the driver.We found this to be much better at diverting a stream of air onto the driver!
Although we have been running this for a few years now, my concern is that we will be asked to blank the hole, as not a period modification!
You can see it in this photo....