I had some of these on my 997 Cab from ZunSport IIRC. On the my current 996TT I am thinking that something similar might be a good idea for country roads. What is the current thinking on this? I see them on GT3s in race situations but wondered how useful they are on road cars and if they impede air flow in our hotter climate in summer? Any suggestions as to sources also (not-US) or even DIY?