Surely if you replace them with the genuine Audi parts then that is all that is required, the whole wiper is rubber and just fits to a pin on the main arm.
The cost of the genuine Audi parts is £11.17 for the LH and £11.02 for the RH according to the Audi web-site.
I must say I find the blades on my new A3 much better than on any other Audi I have owned.