After a little digging in Koup SXR's build thread the wheels are 18x8 with a +48mm offset.
The Rims on Koup SXR's are Fast Wheels "Europa's", they just look like BBS rims.....I'm plannin to get SSR GT2 on my koup.. and sell of my enkei EV5. but will the SSR fit? i know the koup type R is using 18x8.5 BBS, and they claim there is no rubbing. but i dont know the offset of that BBS