Grill and valence block, summer port opening size?

[Formula413]

On my car, I always leave the small upper grill opening open. In the winter I cover the entire lower grill opening, but once ambient temps pass about 50*F I start to see higher than normal temps (normal highway cruising is about 193*F). So I make an opening about the same width as the license plate directly below the actual plate and the temps return to normal. Every car will be different, you will just need to experiment. This is where the SGII is crucial, since most stock temp gauges will not show any fluctuation within the normal operating range. For example, the needle on my temp gauge stops once coolant temp reaches about 190*F, and will sit perfectly still all the way to fan activation at 220*F.

If you want a visual frame of reference for how much airflow my radiator is getting, click on "The Trooper" to the left and you will see a pic of my car. The grill block is not installed in that picture, but you can see the area I am referring to based on the description above.