[Nerys]

there is no optimal CL for a desired CD.

there is an effective CL that is an undesired but necessary CONSEQUENCE of acquiring a CD.

you are also incorrect about ground effect.

tear drop is optimal. the smaller the profile the better.

OPTIMAL is zero drag. 1 dimensional live.

WE NEED to put "stuff" inside it so we have to COMPROMISE DRAG in order to accomodate out needs.

with that compromise on the table the tear drop becomes more ideal (unless you go supersonic then the tear drop is no longer the ideal. Interaction of shock waves etc.. something pointier becomes more ideal but thats not relevant for this discussion.

NOW we have a FURTHER consequence. we MUST have a flat bottom. Why? because we drive on a flat surface so inevitable the bottom of our structures will be flat!

now we are NO LONGER TEAR DROP we are now AIRFOIL. Not because we want to be but as a consequence of our compromises.

all those nice pictures you guys drew of car shapes over a tear drop. Not one of them was a tear drop. that overlay was an AIRFOIL. ie HALF a tear drop. (for an example of a car that is close to more ideal teardrop see the aptera)

another COMPROMISE because of how we wish to USE these shapes.

CL is NOT a desire NOT a want and NEVER GOOD. Period. CL in this case is a CONSEQUENCE of the compromises we had to make to make our machines function and be reasonable to operate and construct.

SO we "accept" some CL as a consequence of these decisions. but it is NOT GOOD and it is NOT HELPING. Its just unavoidable from a practical stand point.

Lift never reduces drag. Period. SHAPE reduces drag the shapes our compromises require us to use as a SIDE EFFECT generate lift UNRELATED to the drag.