getting a hitch fabricated. Do you go down and under the real valence? Do you cut an opening and put a receiver hitch in? Are you going to have a hitch place put your Audi up on a lift and start welding on it? Maybe it's not too scary; I haven't gotten underneath and looked, but those would be the bigger issues to me. I have a 1200lb. boat trailer that I've pulled with a Mazda MX-6 and a 3-series BMW, but I couldn't see doing more than that much weight with an A4.

Good luck