I have a modified roadster, & it's all wrong......
My opinion is frontal is everything in this class, because they all have bodies anything you do before the body proper has little if any effect.
Sp the best approach is the smallest tire / wheel package, smallest body package, do your best to streamline protrusions, and have a good power package. Not much else you can do.
With my car I run tall tires, different track widths, & a '27T body. I would do SOME things differently if I built it today, I just might not say what....