Lug bolt clearance behind hub 2000 Boxster S
 

Not anywhere near my car and unable to verify the space available behind the rear hubs....ordering parts now

Going from 23mm spacers to 15mm to mitigate some rubbing from new tires. Can the same bolts be utilized with 8mm hanging out on the back side of the rotor / hub?

......yes been away all summer doing this:
http://986forum.com/forums/uploads02...1507072007.jpg

On the backs those bolts will most likely hit the parking brake shoes and springs. In the front, probably plenty of room, I can measure next time I take a wheel off and peek behind the rotor if nobody beats me to it.

I believe you are correct sir.....8mm though