These things understeer so badly, I wonder what the results would be to run the wide tires on the front and the narrow tires on the rear? It would sure look goofy (the reason I'll never run this way), and the wide probably won't fit on the front without hitting the cladding anyway. Just food for thought.
There have been discussions on Corvette Forum where a couple of guys have run 315s front and rear in Auto-X with favorable results. Auto-X conditions present hard braking going into very sharp, tight, corners, so a car that is balanced at higher speeds, understeers at low speeds. Hard braking moves the weight bias to the front, increasing understeer. Putting more tire on the front improves the condition.
Another thing I've never seen mentioned with staggered sizes on SyTy AWD is front vs rear tire wear. I had 275/315 on DesertSy. I beat the crap out of that truck and the fronts wore out (evenly across the tread, not alignment) in 15,000 miles. The rears were about 50% worn. Why such a huge difference? With AWD, and the 35/65 split, the fronts are doing 35% of the acceleration work, plus the cornering work. The rears are doing 35% less acceleration work. (Even with matched front/rear sizes, this condition shows up.) Wider rear tires increases the difference in wear even furthur because the wider rear tire has more contact area (in proportion to the front) to distribute the same 65% to the surface.
Stagger wears the fronts at about twice the rate of the rears. Which for those that run 315/35-17 is good, because the only 315 street tire available is a $350 Michelin. The long accepted Sumitomo is out of production.