As I said:
Q. How high up and how far back should my rear wing be?
A. Sometimes technical regulations limit the maximum height and the furthest back a wing may be, but this can still leave room for manoeuvre. Sometimes there are no technical regulations in this respect, in which case the options are infinite. So let’s try and put some more rules of thumb in place where we can, and examine the implications of more open options where we can’t.
In the case of closed saloons/sedans and GT cars that apply maximum height and maximum rearward positions (often related to maximum roof height and the rearmost extent of the vehicle), generally speaking put the wing as high and as far back as you can. This will enable it to work as well as it can by putting it in the ‘cleanest’ air available.