Underside at the rear probably could be improved for airflow

just not sure how practical it is with the exhausts, 4 link live axle etc. Never really looked into it much though.

I'd assume a large front splitter might negate the need for undercar improvements further back, as that should prevent most of the air getting under the car in the first place ?

Although this is getting onto an aero topic rather than standing/rolling start thingy