I agree on covering the air that hits the tires as I have built a C5 Z)6 with Cr World Challenge body and a widebody C6
As well as used dive planes.
My thoughts on this would be to add to the TR splitter and DIY under tray, add and aluminum extension to the splitter sticking much further out and wider then maybe bend the ends up to meet with sections to block the air from the tires.
I am running 15x9 wheels with 225 race tires all around and can go up to at least 245 on the front but already out in the airflow so this would be pretty important for my setup.
I did not think about the Z06 parts, they are cheap, I guess I better order some if wide enough, thanks
Rick