I believe that there are alot of compromises that we can make up for. That's why I got an engine management system, and did alot of the stuff I've done. Also, they have to engineer the cars to be serviceable, and have certain ground clearance. I'm sure that they could easily improve the aerodynamics by alot, if they didn't have to compromise to meet all the criteria. One would probably not hurt the Cd by putting on splitters, underbody smoothness, and such.
I see everything I come to own as an unfinished piece, able to be honed to my specifications. Of course some are more refined than others (I didn't do much to my Mercedes'). One cool thing about the EMS is that I can see by the amount of eintake vacuum, if it's working harder.
The fastest cars I've seen racing had front spoiler extensions that often scraped when braking on bumpy parts. I'd go that route if mine wasn't my daily driver.
BTW, you are lucky that you have your course marked with lines. It rains too much here for that, and I've gotten lost in the middle before
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