I have just brought myself a perspex diffuser with clear straps for £65 on ebay. Seems a nice product although I have yet to use it. I would imagine the faster you go the more turbulance you would get but in the overcrowded roads here in the South I only ever poodle around. I have cruise control on my other car but have only ever used it once and that was outside the South East
Timdon is that the one by Ur windschott? I remember seeing that a long time ago and how it's made of tempered glass similar to a coffee table. I checked the price and ironically it costs the same as a glass coffee table (like 300 euro).
Is there any rattling with the glass? Any strong streams of wind coming from the gap underneath?
Buy a convertible and complain about the wind in your hair ? I've had convertibles all my life and used a deflector once when I noticed it the back of my old z4 , lasted about 10 mins before it went back in the boot .
I added a plexiglass windbreaker to my 1993 Mazda Miata MX-5 and found that it did not make much difference, except to rattle occasionally. When I sold it, the new owner immediately removed it. My 2003 Porsche Boxster S came with a factory installed hard plexiglass windbreak panel which I presume must have worked, as one day I left a hat on the boot when I drove away, and five minutes later noticed that the wind was keeping the hat pressed up against the panel, trying to blow it forward into the cockpit. I stopped, recovered the hat, and made a mental note that the windbreak panel must indeed be of some value on this particular car. My Z4 does not have such a panel, and not even the storage brackets for same in the boot, and it is unlikely that I will add this item.