I have done a bunch of testing with Hoosiers on my SPB (when not racing in class) and grabbed a lap record for TTD at Summit Point doing it. and recorded times well under the standing lap record in TTD/PTD at Watkins Glen (High 2:10 low 2:11 range on used up R6s).
I would not use the R6 255/45/17 at all on a SPB. The gearing is horrible.
The R6 245/40 is what fits best on the 8.5 I have run that on all 4 corners with great results. The car has the same exact balance as with the RA1 255 all around but with higher grip levels and braking. If you are setup to run the RA1 in SPB trim this config is the easiest to switch back and forth to.
The 225/40 R6 is wider than you think but also has a significantly smaller diameter and is lighter to boot. You may find that it works extremely well when used on all four corners giving you a significant gearing advantage.
I would try the 225/40 R6 on all four corners with the 17x7 or with the 17x8.5. I preferred it stretched on the 8.5 as it is extremely crisp on turn in. Your car will sit over 10mm lower on the 225 mounted on the 17x7, even more if stretched on the 8.5.
Best of luck.
-Paul