Just got back from my first autocross in the M2 with the RE71R tires, 275mm square, Hotchkis front bar, wheels as mentioned in above posting.
Warm day, about 85-86 degrees, 2 drivers, smallish concrete surface. Last week I autocrossed the M2 totally stock, on a large concrete surface with impression of some understeer, good turn-in generally, put power down fine.
Today, with the front bar on hole #2 (calling #1 stiffest, #4 softest), the car pushed in a big way. It was frustrating. Couldn't adjust it on grid, no time. Inclined to try on #4 hole next time. Car was much flatter on course, but grip was disappointing.
Now I wonder about the relative stiffness of the Hotchkis bar vs. the Dinan and H&R bars. Externally the dimensions of the Hotchkis and Dinan seem similar, but I have no info on the wall thickness or other factors. All I can say is the front was not a little bit pushy, it was a lotta bit pushy. I guess that's why they call it test and tune
All the tires/wheels had plenty of clearance, especially the 18x9, et 30mm, with 275/35-18 tires. I ran the front tires at 34 psi to 31 psi range. No alignment info, not done yet.
Good thing the sway bar endlinks are pretty easy to adjust (at home).