I installed 25/20 F/R bolt-on spacers from Z1 today, on 2009 with stock springs and Goodyear Eagle F1 tires (245/275 width)
The fronts are flush, but the tires poke a bit on the rears
I think 15mm rears would be better...maybe even 10mm.
I'll see if I can get a shot from the rear to show it better.