I might be blind, but I can't seem to find any reference for a modder settable downforce/speed dependency curve in the physics spreadsheet. It seems like downforce is just fixed at relation to v^2, and of course pitch, ride height, etc. Is there a way to manually set the speed dependence? So that the car can produce downforce at 0 speed? And in effect have a low speed dependency? If I remember correctly this was possible in og rF? (user settable fixed, first order, and second order factors?)
No, the only aero is related to velocity, same in rF1. *(of course, you could increase tyre grip as a way of getting to the right sort of end result)
A 'hack' to simulate the fan cars would be to use diffuser settings to increase downforce compared to other historic cars that should not have a diffuser value. This is not perfect as a fan car should be creating suction even when stationary, which is something diffuser settings cannot achieve. Just using what we have at this time.
TBH, I think rf2 aero model needs rework and/or additional parameters for even current existing cars to get them closer to reality. And since they are only adding downforce heavy cars with focus on endurance racing (now counting Leman Ultimate ) , its getting even more important to update aero physics.