The bigger wheels of stock A5/S5 even RS5 seem to have an offset of much less, around 25 ET, so I would certainly want to test-fit and verify carefully!
Not sure if the spoke would clear the brake caliper, but ET52 is WAY off what you would like on an A5. more like ET25 for something that resembles a flush look. ET52 would make the wheel look incredibly recessed in the arch.