Any of you guys look at the undercarriage parts around the back axle. I am looking at reducing unsprung weight. Ideal would be something lighter than steel. That would balance out the more important weight savings in the front. Also for the preventative maintenance, before the screws all rust. For this A5/S5/RS5 should all fit. and possibly same parts as for the A4 lines.
For example the rear subframe 8K0505235AQ . But also even lighter (weaker) control arms.