+40/25.4 = 1.575"
(9.5" + 1") / 2 = 5.25"
5.25" + 1.575" = 6.825" BS
10.5" - 6.825" = 3.675" FS

So for a 19x9.5" wheel I would have:
FS = 3.675"
BS = 6.825"

Stock A6 S-Line wheel is 18x8 +43
So it would have:
FS = 2.807"
BS = 6.193"

These new wheels would push outward from the stock 8" wide wheel by 0.868" on all four corners which will stick outside the fender by around 11/65" (0.174") of an inch. Inside clearance to the spindle is 1.0625", so I will have 0.4225" clearance from a 9.5" wheel to spindle.

Now depending on how the 3-piece is designed, I would assume you could get at least 2" lip in front and 3" lip in the rear, but if they grind the backing pad, and push the lip forward, they could possibly get an additional 0.5" of lip. But again, depends on the design of the forging and how it clears the caliper. Just not sure how to calculate this part.

What is everyones thought on putting 19x9.5" on all four corners? Has anyone done it yet? Any pics, experiences?

BTW, I am helping my friend out sizing a sweet set of Asanti 123's.

Using the stock wheel, the gap between outer wheel lip and fender lip is 11/16".
With a +40 offset, a 9.5" by my calculation would be 11/64" further than the fender, or 0.174"

There is currently 1.0625 gap between the inner wheel lip and the spindle. With this, a +40 offset and 9.5" wide wheel I would have 0.4225" gap left.