I just finished off a set of RT615K+ 215/45 on 17x8 and liked them enough to buy a fresh set of 215/40 (/45 is too tall). There's a bunch of BRZ/FRS guys at my local track days and most of the run them in the stock size (215/45 x 17?) - everyone likes 'em, esp. since they don't overhead on a 20 minute track session, at least on the lighter cars.