I want to add style and grip to my RS6 performance (2017), that is why got an idea to put different width on Front and Rear wheels.

There is a very interesting set could be like:
- Front: 285/30/R20
- Rear: 325/30/R19
The total height (diameter) of the wheels betweeen fron and rear in 1mm, they are equal.
There are two questions:
1) Do 325 width can be installed on rear axes? Do somebody have such experience?
2) Is it possible to install on front and back wheels with non-equal diameters (height), for example . Front - 285/35/20, Back - 315/30/20?
Thanx in advance!