Welcome to the forum. That's a super clean looking Merc. Thumbs up.
Thumbs up also on your progress to date - 21 to nearly 29 is a massive improvement!
Frontal area calculation methods:
http://forum.ecomodder.com/showthrea...462.html?t=462
http://forum.ecomodder.com/showthread.php?t=82
You can get in the ballpark with (W * H * .84).
http://forum.ecomodder.com/showthrea...5.html?p=21978