I got the idea to do a kind of bodykit as mentioned in the thread title, but I'm struggling on how to do the rear arch, it isn't a coupe so incorporating the doorhandle is not going to be very easy, the doorline itself should not be a problem.
This is what I have so far, any tips are welcome:


HR: https://postimg.cc/dZ1NNM63

Base:


HR: https://s31.wheelsage.org/picture/a/audi/rs_4_avant/audi_rs_4_avant_215.jpeg