I agree, A/C on will have less effect on power than we think. I have left it on during a track session and did not notice it (untill I was black flagged for dripping fluids).

Having the windows up will have more effect than A/C off, great aero advantage. Not, however very safe track practise. I don't think I would want to have a shunt in a vehicle that would prevent the corner workers from pulling me from the car if required (heaven forbid). That is why all touring (production) car series mandate open windows on the drivers side.

When we had a car hit the tire-wall at Daytona, the only way out was through the window. Not much damage to the car but the front fender prevented the door from openning. If the window was up how would they have got the driver out?

Just a thought;

Stan